THE SCIENCE OF 
HYGIENE 

W. C.C.PAKES & A.T. NANKWELL 




Pass "RA 4 30 
Book \ 



The D. Van No&rand Company 

intend this book to be sold to the Public 
at the advertised price, and supply it to 
the Trade on terms which will not allow 
of reduction. 



THE SCIENCE OF HYGIENE 



THE 
SCIENCE OF HYGIENE 

A TEXT-BOOK OF LABORATORY PRACTICE 
FOR PUBLIC HEALTH STUDENTS 

BY .? 

WALTER C: C: PARES 

D.P.H. (CAMB.), F.I.C. 

LATE DEMONSTRATOR OF SANITARY SCIENCE AND BACTERIOLOGIST TO 

guy's HOSPITAL, ETC. ETC. 



NEW EDITION 
REVISED BY 

A^ tI^ankivell 

M.D. (STATE MEDICINE), B.S. LOND., D.P.H. (CAMB.), ETC. 

DEMONSTRATOR OF PUBLIC HEALTH, KING'S COLLEGE, 
UNIVERSITY OF LONDON 



NEW YORK 

D. VAN NOSTRAND COMPANY 

TWENTY-FIVE PARK PLACE 

1912 



t? 



<xV 



99117 



r 



PREFACE TO THE REVISED EDITION 

THIS book is intended for the use of students who are work- 
ing for a diploma in public health ; and it is hoped that 
they will find it useful not only before their examinations, but 
afterwards, should they happen to work again in public health 
laboratories. 

When I was working for my D.P.H. I found the first edition 
of Dr. Pakes' book more valuable than any other text-books on 
laboratory work : the arrangement of the subject matter was 
simple and concise, there was no unnecessary overlapping, and 
what the Author had to say he said plainly and directly. I have 
tried, in this new edition, to attain the same standard of 
excellence. 

All the practical laboratory work, apart from bacteriological 
methods, required by D.P.H. students, is included in this 
volume ; and no effort has been spared to make the book com- 
plete. Many modern text-books have been consulted ; but 
nothing has been merely transferred from these. 

The first edition of this book contained chapters on physics, 
bacteriology, and vital statistics. It was felt, however, that such 
subjects were better treated in other, and necessarily larger, 
books ; and that much of these sciences could hardly be con- 
sidered as laboratory work. For these reasons, no part of this 
volume is devoted to these subjects. 

On the other hand, many additions have been made, and much 
of the text has been re-written. 



vi THE SCIENCE OF HYGIENE 

The illustrations in this volume, which appeared also in the 
first edition, are the admirable work of Dr. T. G. Stevens. 

My thanks are especially due to Dr. A. J. Malcolm, my fellow- 
demonstrator in the Public Health Laboratories of King's College, 
for his help and suggestions. 

A. T. N. 

King's College 

University of London 



CONTENTS 



Water Analysis 










PAGE 

i 


Interpretation of Results . 










35 


Standard Solutions 










59 


Milk Analysis . 










65 


Butter Analysis 










75 


Flour Analysis 










83 


Bread Analysis 










85 


Coffee Analysis 










87 


Spirits Analysis 










89 


Wines Analysis 










9i 


Beer Analysis 










92 


Vinegar Analysis 










93 


Analysis of Air 










95 


Analysis of Soil 










. 106 


Disinfectants . 










in 


Microscopy 










. 116 


Meat Inspection 










. 146 


Appendix 










. 159 


Index . 










162 



LIST OF ILLUSTRATIONS 



FIG. 




I. 


Hempel's Bulb 


2. 


Wheat Starch 


3- 


Barley ,, 


4- 


Rye 


5. 


Potato ,, 


6. 


Arrowroot,, 


7- 


Pea ,, 


8. 


Bean ,, 


9- 


Maize „ 


10. 


Rice ,, 


11. 


Oat 


12. 


Sago ,, 


13. 


Tapioca ,, 


14. 


Calandra Granaria 


IS- 


Acarus Faring 


16. 


Bruchus Pisi 


17. 


Tylenchus Tritici . 


18. 


Penicillium Glaucum 


19. 


Aspergillus 


20. 


Mucor 


21. 


Peronosporon 


22. 


PUCCINIA . 


23. 


USTILAGO SEGETUM . 


24. 


Tilletia Caries 


25. 


>* >> 


26. 


Claviceps Purpurea 


27. 


> ? *i • 


28. 


Butter 


29. 


Margarine 


30. 


Coffee 



PAGE 
96 
Il8 
Il8 
Il8 
II 9 
119 
119 
119 
119 
120 
120 
121 
121 
121 
121 
122 
122 
123 
124 
124 
125 

125 
126 
126 
126 
127 
127 
128 
128 
129 



X 


ThL 


YL bUlJUNUH 


FIG. 




31. 


Chicory 


3 2 - 


> j 




33- 


Tea 




34- 


>> 




35- 


Cocoa 




36. 


Cotton 




37- 


Linen 




38. 


Jute 




39- 


Hemp 




40. 


Wood 




41. 


Wool 




42. 


Silk 




43- 


Pulex Irritans 


44. 


Pulex Penetrans . 


45- 


Cimex 


46. 


Pediculus Capitis . 


47- 


Pediculus Vestimentorum . 


48. 


Pediculus Pubis 


49. 


Acarus Scabei 


50. 


Ixodes Ricinus 


5i. 


Diatoms 


52. 


Desmids 


53- 


VORTICELLA 


54- 


EUGLENA VlRIDIS 


55. 


Spirogeira . 


56. 


Beggiatoa . 


57. 


Volvox 


58. 


Ulothrix . 


59. 


Human Hair 


60. 


Dog's Hair 


61. 


Cow's Hair 


62. 


Rabbit's Hair 


63. 


Amceba 


64. 


Paramecium 


65. 


Daphnia 


66. 


Ova of Worms 


67. 


Trichina Spiralis . 


68. 


> 1 


i j ■ • 



FIG. 
6 9 . 

70. 

71. 

72. 

71- 
74- 
75- 
76. 
77. 
78. 

79. 
80. 



LIST OF ILLUSTRATIONS 
Tenia Mediocanellata 



BOTHRIOCEPHALUS LATUS 



DlSTOMA HEPATICUM 



XI 

PAGE 

153 
153 
153 
154 
155 
155 
155 
158 
158 
158 
158 
158 



THE SCIENCE OF HYGIENE 



WATER ANALYSIS 



COLLECTION OF SAMPLES 

In collecting samples of water for chemical analysis, attention 
should be paid to two points : first, to the cleanliness of the 
vessel in which the water is to be collected ; and, secondly, to 
the actual sample itself. With regard to the first, a glass- 
stoppered Winchester quart bottle is by far the best for a collect- 
ing vessel : this bottle should be thoroughly cleansed. It 
should be well rinsed with strong sulphuric acid, subsequently 
with distilled water until all trace of acid has disappeared, and 
finally with ammonia-free water. The stopper should be replaced 
and tied down but not sealed. In actually collecting the samples 
the bottle should first be filled with the water to be collected and 
emptied, and this should be done a second time. After this a 
true sample should be allowed to run in the bottle if collected 
from a tap, or the bottle should be sunk into the water so 
th^t the mouth is about two inches below the surface if collected 
from & reservoir or river. The water should not fill the bottle, 
but should come just above the shoulder. In sending the water 
to a laboratory for examination, it is convenient, after having 
replaced the glass stopper and tied it down, to place the bottle in 
the well-known baskets made for that purpose. 

With regard to the second point, the actual collection of the 
sample, it should be borne in mind that the sample should really 
be one to test the potentiality for evil of the water in question. 
For instance, if the water is suspected of containing lead, it 
would be obviously unfair to send for analysis the water which 
has been standing for some hours in lead pipes, since the con- 
sumers do not drink this water as a matter of common practice. 



2 WATER ANALYSIS 

In other words, in order to collect a water sample for examina- 
tion, that sample should be such as is ordinarily consumed. 

If the water be one from a reservoir or tank, it should be 
collected as it is flowing from such reservoir or tank into the mains. 

In the case of a well water the same would hold, that is to say, 
the pipe should not be emptied of the water if this is not done 
as a matter of ordinary practice. 

It sometimes happens that owing either to a leaden or leaky 
pipe, the water from a well may be quite good as it comes from 
the well, but bad as it is delivered. In this case it may be 
necessary to examine samples of the water collected from both 
ends of the pipe. Again, the tap is sometimes contaminated, and 
it may be necessary to clean that thoroughly before collecting the 
samples. 

In the case of a river it is obvious that the water may be taken 
from either above or below any sources of contamination or 
pollution that may flow into the river. If therefore we wish to 
analyse such a water, it must be taken into consideration whence 
the water from the river is usually removed for drinking purposes. 
For example, if the intake of a company is at a certain point in 
the river the sample should be collected at a point as near the 
actual intake as possible. 

The water should be examined as soon after collection as 
possible, as there is no doubt that changes do occur after a lapse of 
a short time only, in the water kept even in a well-stoppered bottle. 

This is especially the case with unstable waters, such as 
sewage effluents, or superficial wells liable to pollution. If the 
water therefore has to be transmitted a considerable distance it 
is advisable, wherever possible, to surround the Winchester quart 
with ice. By doing so the changes in the water are retarded, and 
the water as analysed is practically the water as collected. 

The bottle should have a label attached to it. The label 
should bear the following particulars :— 

i. The name and address of sender. 

2. The date of collection of the sample. 

3. Source of water (river, well, etc.). 

If the water is from a well, further details should be added to 
the above : — 

1. The Depth of the well. 

2. The nature of the Geological formation from which the 
water is obtained. 



WATER REPORT 3 

3. Proximity to Sea or Tidal River. 

4. Proximity of Drains, Cess-pools, Manured Lands, or collec- 
tions of decaying organic matter. 

5. Any other details which may seem to bear upon the purity 
of the sample. 

WATER REPORT 

A chemical water report should contain a statement of the 
salts and organic material present in the water. These figures, 
while they afford evidence as to possible pollution, either recent 
or remote, enable us to judge of the general fitness of the water 
for drinking or domestic purposes. 

A considerable amount of confusion has been caused by the 
fact that different analysts return their results in different forms. 
It will be understood that the amount of these materials must, 
in a sample of water, be extremely small. In order therefore to 
state the results without necessitating the use of fractions of a 
milligram, it is usual to express results as parts per 100,000, 
per 1,000,000, per 100,000,000, or in grains per gallon. It may 
be stated that there are advantages in each of these methods. 
In England a fairly large number of analysts still return their 
results in grains per gallon. On the Continent, however, it is 
universally the case that they are reported either in parts per 
100,000 or in parts per 1,000,000. It will be seen therefore that 
reports expressed in parts per 100,000 can be compared with the 
Continental reports without previously converting. 

It is sometimes the custom to express the ammonia in parts 
per 1,000,000 or in parts per 100,000,000, while the rest of the 
report is expressed in parts per 100,000. This method is adopted 
in order that the ammonia should be returned in units and not 
in decimals, but the disadvantage of having two forms of return 
in the same report would appear to be greater than that of 
having the ammonia expressed in decimals. If one accustoms 
oneself to the quantities expressed in parts per 100,000, it is 
merely a matter of remembering that 0*005 * s the limit instead 
of 5. In the following pages, therefore, the results will all be 
tabulated in parts per 100,000. 

When a report is expressed in grains per gallon and it is 
necessary to convert these figures into parts per 100,000, it is 
obviously only necessary to multiply these results by ^-. If, 
on the other hand, we require to convert parts per 100,000 into 



4 WATER ANALYSIS 

grains per gallon, it is necessary only to multiply by 07. The 
reasons for this, of course, are that there are 100,000 grammes in 
100,000 c.c. and 70,000 grains in a gallon. 



PHYSICAL CHARACTERS 

Before proceeding to the analysis of the water by the various 
chemical methods which are adopted, it is generally necessary to 
make some preliminary observations on the physical characters of 
the sample. 

1. Turbidity. Waters vary somewhat in the amount of 
turbidity they show, although as a rule the best waters are per- 
fectly clear. It is of course possible that a perfectly safe 
drinking water might have been rendered turbid through the 
shaking up with it of some mineral matter, but, speaking generally, 
a water that shows any marked turbidity will prove, upon 
further examination, to be unfit for drinking purposes. One 
expresses the degrees of turbidity as " clear," " slightly turbid," 
or "very turbid," the last applying more especially to sewage or 
sewage effluents. 

2. The next point to be considered is the colour. 

In order to determine the colour it is necessary first of all to 
allow any sediment to deposit. The clear supernatant water is 
then poured into what is known as a two-foot tube. This consists 
of a glass cylinder, at each end of which a piece of plate glass 
is screwed. When the water is poured in, the plate which has 
been removed in order to allow of this should be screwed down, 
and the whole apparatus carefully wiped. The eye should then 
be placed at one end, and at the other a white porcelain slip or 
piece of paper. Good waters are generally slightly blue when 
seen through this tube; if there is any yellowish or brownish 
colour, there will be some suspicion of sewage contamination 
unless the water happens to have been collected from a peaty 
soil. Occasionally the water possesses a decidedly green colour 
owing to the presence of the green algae, which are of course, in 
themselves, harmless. 

3. Taste. This is by no means a valuable test; the pleasant 
taste of a water is generally due to the solution of gases, and 
even the best of waters when not aerated are insipid. When it 
is remembered that a smaller quantity of sodium chloride than 
75 grains to the gallon or 100 grammes to the 100,000 cannot be 



PHYSICAL CHARACTERS 5 

tasted, it will be seen of what little worth the taste is. Some 
algae, however, when they decompose liberate volatile oils, of 
which even a trace may cause a water to taste and smell unplea- 
santly. Such algae are found chiefly in reservoirs and filter beds : 
their decomposition products, although they make the water 
objectionable, do not seem to make it, in any way, dangerous to 
health. 

4. Smell. A good drinking water should, of course, be 
absolutely inodorous. If there is a marked degree of contamina- 
tion, or the water has been collected from a peaty soil or from 
the neighbourhood of some dye or chemical works, it is possible 
that the water may possess some odour. It by no means follows, 
however, that a water which is so contaminated as to be utterly 
unfit to drink possesses any odour at all. 

In order to detect the odour, the most convenient method is to 
place about 250 c.c. in a glass-stoppered bottle, which is then 
placed in a water bath or oven at about 30 C. for a few minutes. 
The stopper should then be removed and the nose applied to the 
bottle at once. This is necessary, since the odour is extremely 
evanescent. 

5. As has been before stated, a palatable water is well 
aerated. In order to test this properly it is generally only 
necessary to pour some of the water into an open beaker, and 
notice the evolution of small bubbles of gas. This test is of no 
value as regards the fitness of the water for drinking purposes, 
but is merely evidence of its palatability. 

6. Reaction. The reaction of most drinking waters is 
alkaline. Occasionally a drinking water is found to be acid, and 
is then held not to be suitable for a water-supply because of the 
facility with which it takes up lead. This has been found to be 
the great objection to the Yorkshire moor supply for Sheffield, 
etc. Such a water derived from peaty soil contains humic and 
ulmic acids. The alkalinity or acidity of a water in itself is no 
criterion of the pollution of the water by sewage, since most 
waters which are highly contaminated by sewage still retain their 
alkalinity. The waters drawn from the neighbourhood of dye or 
chemical works are sometimes acid, but other criteria of their un- 
suitability for drinking purposes will be found on further analysis. 

7. The Sediment. As has been before stated, a good water 
should contain no sediment, but the mere presence of a slight 
sediment will not necessarily condemn the water. The sediment 
may consist either wholly of mineral matter, or of vegetable 



6 WATER ANALYSIS 

matter, or of both. Its nature is generally discovered by micro- 
scopical examination, and will be treated under that head. 



TOTAL SOLIDS 
Apparatus required 
i. A platinum dish. 

2. A flask graduated at 200 c.c. 

3. A water bath. 

4. A water oven. 

5. A desiccating chamber. 

6. A balance which will turn to ^ of a milligram. 

The Process 

In a clear water with no sediment it is obvious that the solids 
will be those in solution. In turbid waters the total solids may 
be either those in solution plus those in suspension, or those in 
solution alone. Most analysts determine the total solids in 
solution ; if, therefore, the water is turbid, it must be allowed to 
sediment, or must be filtered before proceeding with the deter- 
mination. 

1. 200 c.c. of the clear water should be measured out into the 

graduated flask. 

2. The platinum dish should be thoroughly w r ell cleansed with 

HC1, and subsequently with distilled water ; then heated in 
the Bunsen flame and placed in the desiccator over H 2 S0 4 
until it is cold. It must then be weighed, and a note of its 
weight taken. 

3. Into the dish as much of the 200 c.c. as it will conveniently 

hold is poured. The dish is then placed over a water bath 
and covered with an inverted funnel in order to protect the 
contents from the dust. From time to time more water is 
added until the whole of the 200 c.c. has been evaporated 
to dryness. 

4. The dish with the evaporated contents is now removed from 

the water bath and placed in the water oven and kept at 
ioo° C. for from 20 minutes to half an hour. 

5. Now remove the dish from the oven and place it in the 

desiccator over H 2 S0 4 until it is cool. 

6. Now weigh it carefully two or three times, replacing it in the 

desiccator for 5 or 10 minutes between each weighing. 



TOTAL SOLIDS 7 

Instead of heating the dish in the water oven at ioo° C some 
analysts heat it in an air oven at 120 C. This latter method 
ensures the disappearance of the water of crystallization from any 
of the salts which may be present with their water of crystalliza- 
tion in the residue evaporated at ioo° C. 

EXAMPLE 
Weight of dish .... 29-7834 

„ of residue of 200 c.c. of water + dish 30-0030 



Weight of residue . . . .0-2196 

.*. Total solids per 100,000 = 0-2196x500=109-800 

Notes 

If it is necessary to determine the total solids in a short time, 
a less quantity of water than 200 c.c. may be taken ; but as the 
residue is sometimes only very small the error of experiment 
must necessarily be greater. In a sample of water which is 
known to be very hard, or to be very saline, 100 c.c. will be 
ample. 

LOSS ON IGNITION 

After the total solids have been ascertained, the platinum dish 
containing the residue is heated over the flame of a Bunsen 
burner to a white heat for some time, allowed to cool and re- 
weighed. The loss in weight is then recorded as Loss on 
Ignition. 

Whilst the solids are being ignited, blackening will take place 
if much organic matter is present, and this fact should be noted. 

The loss on ignition represents to a large extent the organic 
matter present, since the ignition causes this to be oxidized, and 
C0 2 and H 2 to be given off. It is not, however, altogether 
a measure of the amount of organic matter, since the water of 
crystallization and the ammonium salts are also driven off. 

EXAMPLE 

Weight of dish + total solids . . 30*0030 grammes 

,, ,, + total solids (after ignition) 29*9939 ,, 



Loss on ignition (200 c.c.) . . . 0*0091 gramme 

.*. Loss on ignition per 100,000 = 4*55 grammes. 



8 WATER ANALYSIS 

ESTIMATION OF CHLORIDES 
Apparatus, etc., required 

i. A white porcelain evaporating dish. 

2. A small glass stirring rod. 

3. A 50 c.c. pipette. 

4. A burette graduated ino'i c.c. 

5. Potassium chromate solution. 

6. Standard silver nitrate solution. 

The Process 

1. Fill the burette with the standard silver solution. 

2. Measure 50 c.c. of the water to be examined in the graduated 

pipette and run it into the white evaporating dish. 

3. Add one or two drops of the solution of K 2 Cr0 4 to the water 

and stir. 

4. Allow the silver solution to run into the water drop by drop 

until the evanescent brown colour remains. 

5. Read off the height of the solution in the burette and note it. 

Explanation of the Process 

When a solution of silver nitrate is added to an alkaline solu- 
tion of a chromate a reddish brown precipitate of silver chromate 
is formed. If, however, any chloride is present, the silver will 
combine with this chloride before it combines with the chromate. 
The interactions taking place are expressed by the following 
equations : — 

NaCl + AgN0 3 - NaN0 3 + AgCl 
K 2 Cr0 4 + 2 AgN0 3 = 2 KN0 3 + Ag 2 Cr0 4 

When, therefore, the permanent brown precipitate is formed, all 
the chloride will have combined with the silver, and the amount 
of the silver used at this juncture will be a measure of the 
chlorides present in the water. 



EXAMPLE 




1 st reading of burette 


. 6*6 c.c 


2nd „ „ . . 


■ 8-9 „ 



Amount of silver used . . 2*3 



TOTAL HARDNESS 9 

Now 1 c.c. of silver nitrate solution = 1 milligram of chlorine 

• • 2 3 >i >» = 2 3 5 j >> 

But this quantity was present in 50 c.c. of the water 

.'. in 100 c.c. there will be 4*6 milligrams of chlorine 

i.e. there will be 4*6 parts of chlorine in 100,000 parts of water. 

The quantity of chlorine is frequently expressed in terms of 

NaCl as well as in terms of CI itself. In order to express the CI 

in terms of NaCl it is only necessary to multiply the weight of CI 

by — -$. In our example we found that 4*6 parts of CI were 

35*5 
present. Expressed as NaCl this will be 1*648 x 4*6= 7*5 parts. 

Our report should read : — 

Chlorine .... 4*6 parts per 100,000 
Expressed in NaCl . . . 7*5 „ ,, 

Notes 

The estimation should always be repeated. If we know when 
to expect the " end point," we are able to estimate more easily 
the exact point when the colour changes. 

Before filling the burette it must be scrupulously clean. A 
new burette should be washed out with strong sulphuric acid 
and subsequently with distilled water until all traces of the acid 
have disappeared. After it is clean, a few c.c. of the solution 
should be poured in and (holding it horizontally) allowed to 
run over the whole of the surface. The burette must be emptied 
and filled with the solution. A few drops must now be allowed 
to run out, in order to fill the nozzle, and any drop which hangs 
on the nozzle must be removed. The height of the fluid in the 
burette must be carefully read and noted. In the case of colour- 
less fluids it is customary to read off the division of the scale 
which corresponds to the bottom of the meniscus. In the case 
of indigo, however, it is convenient to read off the division of 
the scale which corresponds to the top of the meniscus. 

TOTAL HARDNESS 
Apparatus, etc., required 

1. A small glass-stoppered bottle (about 125 c.c. capacity). 

2. A burette graduated in tenths of a c.c. 

3. An Erlenmeyer flask. 

4. A 50 c.c. pipette. 

5. A 100 c.c. measure graduated in c.c. 

6. Standard soap solution. 



io WATER ANALYSIS 

The Process 

i. Fill the burette with the standard soap solution, and read off 
the height. 

2. Measure 50 c.c. of recently boiled distilled water into the 

bottle. 

3. Add o'5 c.c. of soap, replace the stopper, and shake the 

bottle well. Add more soap, a few drops at a time, until a 
permanent lather is formed after brisk shaking. 

4. Read off the height of the soap in the burette. 

The difference between the two readings will be the amount 
of soap required to form a lather with perfectly soft water. 

{Note. — It is well for a beginner to do this several times before 
he begins to try to determine the hardness, so as to familiarize 
himself with the appearance of a permanent lather, and in order 
that he may find for himself the amount of soap which must 
subsequently be deducted from that used to form a lather with 
the water under examination.) 

After having done this, proceed to the examination of the water. 

1. By means of the 50 c.c. pipette, run 50 c.c. of the water into 

the bottle. 

2. Add 1 c.c. or less of the standard soap at a time to the water 

and shake well. When a certain amount of the soap has 
been added, the lather, which is at first very transient, 
begins to remain for a short time. When this point has 
been reached, the soap must be added only a few drops at 
a time, in order not to overshoot the mark. 

3. When sufficient soap has been added the bubbles on the 

surface of the water will break very slowly ; the bottle 
should then be laid on its side for five minutes. If at the 
end of this time the lather is still present, even if it is 
diminished in thickness, the estimation is done, and it only 
remains to read off the height of the soap in the burette, 
and deduct from it the height observed before beginning 
the estimation. The difference will be the amount of soap 
required, and from this is calculated the hardness. 

Explanation 

A soap is a salt, the base of which is a metal and the acid one 
of the fatty acids. Some of these salts, as those of sodium and 
potassium, are soluble in water, and when rubbed up with or 



TOTAL HARDNESS n 

shaken up in water cause a lather. Others, such as those of 
calcium and magnesium, are insoluble in water, and therefore are 
precipitated ; being precipitated, they are incapable of forming a 
lather. If a soluble calcium salt is present in water and a 
solution of a sodium soap is added, the insoluble calcium soap 
is formed. 

The cause of hardness in water is the presence in it of soluble 
salts of calcium and magnesium. So long as either of these 
salts exists unprecipitated in the water, it will be impossible to 
form a lather. Directly they have been precipitated only a 
slight addition of soap is required to form a lather. The amount 
of soap required to form a lather is therefore the measure of the 
amount of the salts of calcium and magnesium present in the 
water. 

EXAMPLE 

It was found that it took o-8 c.c. of the soap solution to form 
a lather with 50 c.c. of distilled water. 

The sample of water to be examined took 7*6 c.c. of soap to 
form a lather with 50 c.c. 

50 c.c. sample required . . . 7 '6 c.c. soap 

50 c.c. distilled „ . . o*8 „ ,, 

Soap solution required to precipitate Ca and Mg salts = 6*8 c.c. 

But 1 c.c. of the Standard soap solution = 1 milligram of CaC0 3 . 

.'. 50 c.c. of the water contain 6*8 milligrams of Ca and Mg 
(expressed as CaC0 3 ). 

.". 100 c.c. of the water contain 13*6 milligrams. 

In other words, the sample has a hardness of 136 parts per 
100,000. 

Notes 

It will have been noticed that the hardness is expressed in 
terms of CaC0 3 , whether it is due to calcium or magnesium. 
This is merely for convenience, so that one need only have one 
standard solution. As a matter of fact, more soap is required to 
form a lather with a certain amount of magnesium than is required 
for an equivalent quantity of calcium. 

The soap solution does not remain permanently of the same 
strength. After the lapse of a certain time it undergoes certain 
changes and becomes weaker. Unfortunately this change does 
not show any degree of constancy. The solution may remain up 
to standard for weeks, and then suddenly change. 

In order, therefore, to ascertain the hardness of any sample 



12 WATER ANALYSIS 

of water with great accuracy, three determinations should be 

made : — 

i. The soap required to lather 50 c.c. of distilled water. 

2. The soap required to lather 50 c.c. of distilled water contain- 

ing 6 c.c. of the standard calcium solution. 

3. The soap required to lather 50 c.c. of the sample. 

EXAMPLE 

No. 1 required . i'oc.c. 

No. 2 „ . 8 '4 „ 

No. 3 „ . 15*6 „ (diluted 1 in 2 took 7 '8 c.c.) 

6 c.c. Ca solution required . 8*4- 1= 7*4 c.c. 

Hardness in sample „ . 15*6-1 = 14*6 „ 

But 7*4 c.c. of soap solution = 6 milligrams of CaC0 3 . 

.'. 14*6 c.c. ,, ,, = — — of 6 milligrams of CaC0 3 

= 1 1 *8 milligrams of CaC0 3 . 
Thus 50 c.c. of the sample contain ir8 „ „ 

and 100 c.c. „ _ „ 23*6 „ „ 

.'. 100,000 parts contain 23*6 parts of hardness,, expressed as 
CaC0 3 . 

PERMANENT HARDNESS 

Hardness is spoken of as either temporary or permanent. The 
former consists of calcium bicarbonate and is held in solution by 
the carbonic acid in the water. When the carbonic acid is 
expelled from the water as by boiling, the bicarbonate is con- 
verted into the carbonate and is at the same time precipitated, 
as it is insoluble in water. 

Ca(HC0 3 ) 2 = CaC0 3 + H 2 + C0 2 

The permanent hardness is due to the sulphates, chlorides, and 
nitrates of calcium and magnesium, and these are unaffected by 
boiling. 

The Process 

1. Measure 100 c.c. of the water to be examined in a graduated 

cylinder and pour it into an Erlenmeyer flask. 

2. Boil over a piece of wire gauze until the bulk is reduced to 

about one-half. 

3. Allow it to cool and filter through a hard white filter-paper 

which has been well washed with distilled water. 



FREE AMMONIA 13 

4. Make up the volume to 100 c.c. with distilled water. 

5. Take 50 c.c. of this and estimate the hardness as before. 

This estimation is also expressed in terms of CaC0 3 . 
Having estimated the total and the permanent hardness, the 
difference will obviously be the temporary hardness. 

Notes 

The hardness is expressed in grains per gallon (degrees), or in 
parts per 100,000 of CaC0 3 . Although this does not represent 
the actual truth, since other salts have their share in producing 
this hardness, it is an expression for the factor of practical 
importance, i.e. the soap-destroying power of the water. 

In laundry work the whole work of the water used exercises its 
soap-destroying power, and it is only when the soap is in excess 
of this, that the detergent action of the latter begins. 

It will occur to the reader that in washing one's hands, only 
the small quantity of water adhering to the hands need affect the 
soap, before a lather is obtained. Therefore it is possible to 
wash the hands with comfort in a much harder water than can be 
used in the laundry without a great waste of soap. 



FREE OR SALINE AMMONIA 
Apparatus, etc., required 

1. A-32-ounce glass retort, or a long-necked two-litre glass 

flask. 

2. A condenser. 

3. Clamps and burner. 

4. 12 Nessler glasses to hold 100 c.c. with a graduation at 50 c.c. 

5. White glazed porcelain slab. 

6. 50 c.c. burette graduated in tenths of a c.c. 

7. 200 c.c. Erlenmeyer flask. 

8. A 2 c.c. pipette. 

9. Nessler's reagent. 

10. Standard solution of Ammonia (1 c.c. = o-oi milligram of 
NH 3 ). 

Before beginning the process for the estimation of ammonia it 
is advisable to practise the method first on known quantities 
of ammonia added to water, and secondly on unknown quantities 
which are also added to the water. 



i 4 WATER ANALYSIS 

i. In order to do this add i c.c, 2, 3, etc., up to 10 and 15 c.c. 
of the standard ammonia solution to each of ten of the 
Nessler glasses, fill each up to the 50 c.c. mark with distilled 
ammonia-free water, and add 2 c.c. of Nessler's solution. 
Allow this to stand for two minutes after well shaking. 

2. Compare these tints carefully in order to get an idea of the 

depth of tint produced by the varying quantities of ammonia. 
After having become familiar with these tints, add a small 
unknown quantity of ammonia to the 50 c.c. of distilled 
water in a Nessler glass and estimate the amount added. 

3. Repeat this several times in order to get an idea of the 

approximate amount of ammonia which a certain tint 
indicates. 

Suppose that we find that 5 c.c. of the standard ammonia 
solution gives a darker tint than the unknown quantity, we 
add 3 c.c. and find this too little ; next we add 4 c.c. and 
also find this too little ; the addition of 4*5 exactly matches, 
that is to say, our unknown quantity contains the equivalent 
of 4*5 c.c. of the standard ammonia solution. As the standard 
ammonia contains o'oi milligram per c.c. it is evident that 
the 50 c.c. of water contains 4*5 x •01=0*45 milligrams. There 
is another method of determining the amount present in a 
Nessler glass when the tint cannot be exactly matched by 
any of the standard solutions we have made. For example, 
the unknown quantity is found to be less than the equivalent 
of 5 c.c. of the standard ammonia. By means of a clean 
pipette remove some of the fluid in the standard solution until, 
when both glasses are looked at from above over the white slab, 
the tints are exactly alike ; next measure the fluids left. Suppose 
35 c.c. are left of the standard solution, and match 50 c.c. of the 
test solution ; then the ammonia in the test-glass equals f£ of 
the standard. But the standard contains 5 c.c. of the ammonia 
solution ; therefore the test-glass contains |~§- of 0*05 milligrams 
of NH 3 , and this equals 0*035 milligrams of ammonia. 

If the fluid contained in the test-glass is deeper than that in 
the standard glass with the 5 c.c. of the ammonia solution, some 
of the fluid from the test-glass must now be removed until the 
tints are exactly alike. Suppose 10 c.c. have to be removed, 
then 40 of the test equal 50 of the standard ; therefore 50 of the 
sample equal |§ of 50 c.c. of the standard. But the standard 
contains 0*05 milligrams of ammonia; therefore our test contains 
0*0625 milligrams of ammonia. 



FREE AMMONIA 15 

The Process 

1. Rinse out the retort or flask with strong HC1, and subsequently 

with good tap water, until all traces of the acid have disap- 
peared, then rinse out well with two or three lots of distilled 
ammonia-free water and empty. 

2. Fix the retort or flask in a good clamp and attach [the con- 

denser, which is also supported by a clamp. 

3. When the retort and condenser are fitted together, connect 

the outside case of the condenser with the water tap, re- 
membering to connect it in such a way that the water runs 
in from below upwards. Do not turn on the tap yet. 

4. Pour about 500 c.c. of ammonia-free distilled water into the 

flask or retort, add a few grains of pure sodium carbonate 
and a few pieces of broken pumice. The latter will prevent 
" bumping." Light the burner and put it under the flask, 
the bottom of which should be protected with wire gauze. 

5. Distil until the steam has issued from the lower end of the 

condenser for several minutes, and then turn on the water 
through the outer casing of the condenser. 

6. Collect about 2ooc.c.ofthewater,andaseach 50 c.c. comes over 

add 2 c.c. of Nessler. If the condenser and retort are perfectly 
clean there will be no colour in the third or fourth distillates. 

7. After thus cleaning the condenser and flask, add 500 c.c. of 

the water to be examined. The small amount of Na 2 C0 3 
present in the flask will neutralize any acid in the sample 
water, and leave the ammonia free to be distilled off. Re- 
place the stopper or cork and begin to distil. 

8. Distil over 50 c.c. into a Nessler glass. When this is done 

collect the next distillate in a fresh Nessler glass and add 
2 c.c. of Nessler to the first distillate. If a colour is 
developed upon the addition of the Nessler, determine the 
amount of ammonia present as explained above. When 
the second Nessler glass is full remove that and place the 
third. Add 2 c.c. of Nessler to the second distillate and if 
there is still a colour produced determine the amount of 
ammonia in the second distillate. Continue to do this until 
the addition of Nessler to the distillate produces no colour. 
(It is generally found that the whole of the saline ammonia 
comes off in the first 150 c.c. of the distillate, so that one 
always expects to find no ammonia in the fourth 50 c.c. 
distilled over.) 



16 WATER ANALYSIS 

9. Having determined the quantity of ammonia present in each 
of the distillates, add these quantities together and it will 
represent the quantity of saline ammonia present in 500 c.c. 
of the water. From this the amount present can be readily 
expressed in parts per 100,000. 

EXAMPLE 

The first distillate of 50 c.c. was matched by 1*5 c.c. of 
standard NH 3 . 

The second distillate of 50 c.c. was matched by i*o c.c. of 
standard NH 3 . 

The third distillate of 50 c.c. was matched by 0*5 c.c. of 
standard NH 3 . 

The fourth distillate gave no colour with Nessler's solution. 
.\ the three distillates, or all the free and saline ammonia in the 
500 c.c, were matched by 3 c.c. of the standard NH 3 solution. 

In other words, 500 c.c. contained 0*03 milligrams of ammonia. 
.'. 100 „ ») 0*006 „ „ _ „ 

Or there were *oo6 parts of free and saline ammonia in 100,000 
parts of the sample. 

ALBUMINOID AMMONIA 

The Process 

1. While the saline ammonia is being distilled off, 50 c.c. of the 

alkaline permanganate solution should be poured into an 
Erlenmeyer flask and about 150 c.c. of ammonia-free water 
added. This must now be boiled until the bulk is reduced 
to 100 c.c. 

2. When all the free and saline ammonia has been distilled off 

and the distillation stopped, the alkaline permanganate is 
poured carefully into the flask or retort, the stopper is re- 
placed, and the distillation begun again. 

3. As the water comes off it should be collected in the Nessler 

glasses as before, and the Nessler reagent added. 

4. The quantity of ammonia must be estimated as in the case of 

the saline ammonia. 

Explanation 

The nitrogenous matter in the water is reduced by boiling with 
alkaline permanganate, and converted into ammonia, which is 
distilled off. 



TESTS FOR NITRITES 17 

Notes 

The preliminary boiling of the permanganate ensures the 
absence of both ammonia and organic matter, and therefore all 
the ammonia distilled over must come from the water under 
examination. 

The organic matter is not all reduced instantaneously, but more 
or less gradually. The ammonia does not therefore come off 
necessarily in the first 150 c.c. of the distillate as does the saline 
ammonia. 

Every 50 c.c. of water as it comes off must therefore be tested 
with Nessler reagent until there is no reaction. 

If a sample of water contains a considerable quantity of 
organic matter, it sometimes happens that there is a danger of 
the retort boiling almost dry. When this occurs 100 or 200 c.c. 
of organically pure ammonia-free water must be added to the 
retort, and the distillation continued. 



TESTS FOR THE PRESENCE OF NITRITES 
BY POTASSIUM IODIDE AND STARCH 

Apparatus, etc., required 

1. Two Nessler glasses. 

2. Potassium iodide solution. 

3. Starch solution. 

4. Dilute sulphuric acid (about 10%). 

1. Pour 50 c.c. of the water to be tested in a Nessler glass and 

50 c.c. of distilled water into another. 

2. Add a few drops of the KI solution to each of the Nessler 

glasses and then a few drops of the starch solution. 

3. Add a few drops of dilute sulphuric acid to each tube. 

If nitrites are present, a blue colour will be immediately 
formed, the depth of the colour depending on the amount of 
nitrites present. 

Explanation 

The sulphuric acid liberates nitrous acid from the nitrites. 
The free nitrous acid then liberates iodine from the potassium 
iodide, and this iodine combines with the starch and gives the 
blue colour 

This is an extremely easy method of determining the presence 



18 WATER ANALYSIS 

of nitrites, but care must be taken to make the observations at 
once, since nitrates may give the same reaction after the lapse of 
a short interval. 

BY METAPHENYLENE-DIAMINE-HYDROCHLORIDE 

GRIESS'S METHOD 

Apparatus required 

i. Two Nessler glasses. 

2. Solution of metaphenylene-diamine-hydrochloride. 
i. Pour 50 c.c. of the water to be tested into a Nessler glass, and 

50 c.c. of distilled water into another. 
2. Add to each glass 1 c.c. of the solution of metaphenylene- 

diamine-hydrochloride, and a few drops of hydrochloric 

acid. 
If nitrites are present a brown colour will be formed in the 
sample, due to the production of Bismarck Brown. 

Explanation 

Metaphenylene-diamine-hydrochloride is a colourless solution 
which in the presence of nitrous acid gives rise to triamido-azo- 
benzol or Bismarck Brown, and hence colours the solution. The 
hydrochloric acid is added to liberate nitrous acid from the 
Nitrites present in the water. 

2 C 6 H 4 (NH 9 ) - HC1 + HN0 2 = 

C 6 H 4 'NH 2 -N : NC 6 H 3 (NH 2 ) 2 ■ HC1 + 2 H 2 

Notes 

Metaphenylene-diamine-hydrochloride, when dissolved in water, 
tends to become dark in colour, and this interferes with the 
delicacy of the test. The solution is better when made fresh ; 
failing this it must be filtered through animal charcoal until it is 
colourless. 

QUANTITATIVE ESTIMATION OF NITRITES 
GRIESS'S METHOD 

Apparatus required 

1. Nessler glasses. 

2. Solution of metaphenylene-diamine-hydrochloride. 

3. Standard nitrite solution. 



TESTS FOR NITRATES 19 

The Process 

1. Into each often Nessler glasses put varying amounts of the 

standard nitrite solution — 1 c.c, 2 c.c., etc., to 10 c.c. 

2. Fill each glass up to the 50 c.c. mark with distilled water. 

Add to each a few drops of HC1. 

3. Add 50 c.c. of the sample water to another Nessler glass, 

together with a few drops of HC1. 

4. Add 1 c.c. of metaphenylene-diamine-hydrochloride solution 

to each glass. 

5. Compare the various tints, and see with which of the ten 

glasses the sample water matches. 

6. If the sample is too dark, dilute with twice or more times the 

volume of distilled water and repeat the process from the 
beginning. 

EXAMPLE 

It was found that the Nessler glass containing the sample 
.water matched the Nessler glass in which there were 5 c.c. of 
the standard nitrite solution. 

Now 1 c.c. of the standard nitrite solution = '01 milligrams 
of N 2 as nitrite. 

.". 5 c.c. of the standard nitrite solution = 0*05 milligrams 
of N 2 as nitrite. 

Thus in 50 c.c. of the water under examination there were 
0*05 milligrams of N 2 as nitrite. 

So in 100 c.c. there were o*i milligrams of N 2 as nitrite, or, 
in other words, o*i part per 100,000. 

Notes 

Griess's method estimates nitrites alone. 

The principle involved is the same as in Nessler's method of 
estimating ammonia, and the student will find that when he has 
mastered the one method the other will come easily to him. 

TESTS FOR THE PRESENCE OF NITRATES 

BRUCINE METHOD 

1. 2 c.c. of the suspected water are placed in a perfectly clean 

white porcelain dish and evaporated to dryness. 

2. A drop of pure H 2 S0 4 is allowed to drop on the residue. 

3. A minute crystal of Brucine is now added. 



20 WATER ANALYSIS 

If nitrates are present, a pink colour will appear. This test 
is an extremely delicate one, a reaction being obtained when the 
nitrate is present in the proportion of only i in 10,000,000. 



DIPHENYLAMINE TEST 

1. A few crystals of diphenylamine are put into a porcelain dish. 

2. 1 c.c. of pure H. 2 S0 4 is added. 

3. A little of the suspected water is poured into the dish. If 

nitrates are present a blue colour will appear. Nitrites 
give no colour with this test. 



BY POTASSIUM IODIDE AND STARCH 

The method is the same as in testing for nitrites, and is of no 
use for detecting the presence of nitrates if the nitrites are also 
there. If, however, no colour comes at once, but does come 
after the lapse of a few minutes, it may be inferred that nitrates, 
and not nitrites, are present in the water. The test, however, is 
not so satisfactory as those already mentioned. 

QUANTITATIVE ESTIMATION OF NITRATES 
PHENOL-SULPHONIC ACID METHOD 

Apparatus, etc., required 

1. Evaporating dishes. 

2. Nessler glasses. 

3. Phenol-sulphonic acid solution. 

4. Standard nitrate solution. 

The Process 

1. Place 10 c.c. of water in the dish and evaporate to dryness on 

the water bath. 

2. Place in another dish 1 c.c. of the standard nitrate solution 

and evaporate to dryness in the same manner. 

3. To each of the dried residues add 1 c.c. of phenol-sulphonic 

acid, 1 c.c. of distilled water, and 2 or 3 drops of sul- 
phuric acid. 

4. Warm gently over the water bath. 

5. Distilled water is now added and excess of ammonia, and the 

bulk of each is made up to 100 c.c. 



NITRATES AND NITRITES 21 

6. 50 c.c. of the solutions are pipetted into two Nessler glasses. 

7. Compare the tints and pipette off from the darker tinted glass 

as much of the water as is necessary to make the tints alike 
when viewed from above. 

8. Calculate from the quantities remaining in the glasses the 

amount of nitrate present. 

Explanation 

The nitrates present in the water convert the phenol-sulphonic 
acid into a mixture of nitro compounds, the chief of which is 
trinitrophenol, the ammonium salts of which are coloured. 

C fi H 4 (OH)S0 3 H + 3HN0 3 -C 6 H 2 (OH)(N0 2 ) 3 + H 2 S0 4 +2H 2 

The depth of the colour is then a measure of the amount of 
these compounds present, and so of the nitrates originally present 
in the water. 

Notes 

The phenol-sulphonic acid method estimates nitrates alone. 
It cannot be used for the estimation of nitrates if the water under 
examination contains much organic matter (as, for example, does 
a sewage effluent), because such organic matter gives much 
charring when the water is evaporated, and so interferes with 
the colour of the trinitrophenol. In such a case one of the 
following methods which estimate both nitrites and nitrates must 
be employed, and when the result is obtained the nitrate value 
of the water is determined by subtracting from the result the 
figure for nitrites obtained by Griess's method, the remainder, 
of course, being the amount of nitrates present. 

QUANTITATIVE ESTIMATION OF NITRITES 
AND NITRATES 

I. INDIGO METHOD 

Apparatus, etc., required 

1. A small beaker holding about 60 c.c. 

2. A small glass stirring rod. 

3. A 20 c.c. pipette. 

4. A graduated glass cylinder to hold' 20 c.c. 

5. A burette graduated in o*i c.c. 

6. Pure redistilled nitrate-free concentrated sulphuric acid. 

7. Standard indigo solution. 



22 WATER ANALYSIS 

The Process 

i. Fill the burette with the standard indigo, and make a note of 
the height of the indigo, reading the top of the meniscus. 

2. Pipette 20 c.c. of the water into the beaker, taking care to 

drain the pipette. 

3. Measure 20 c.c. of H 2 S0 4 in the cylinder. 

4. Pour the H 2 S0 4 into the beaker, stirring briskly, and do not 

wait for the last drops of the acid to drain. 

5. At once allow the indigo to run into the now hot mixture drop 

by drop, until the greenish evanescent colour becomes per- 
manent. 

6. Read off the height of the indigo in the burette. 

The estimation must now be repeated, in a slightly different 
order, as follows: — 

1. Pipette the 20 c.c. of water into the beaker. 

2. Allow about o"5 c.c. less of the indigo than was required in 

the first estimation to run into the beaker. 

3. Now pour in the H 2 S0 4 , and stir briskly. 

4. Immediately the colour is discharged, add more indigo drop 

by drop, until the colour is once more permanent. 

5. Now read off the height of the indigo. 

Explanation 

The concentrated H 2 S0 4 decomposes the nitrites and nitrates 
present and liberates free nitric acid. This then oxidizes the 
indigo, forming isatin, which is colourless. Directly all the 
nitric acid has been used up a further addition of indigo will not 
be oxidized and will therefore retain its colour. The amount of 
indigo required to give a permanent colour will indicate the 
quantity of nitrates and nitrites present in the 20 c.c. of water. 

EXAMPLE 

A second or control estimation gave the following : — 

1 st reading of burette . . . 10*3 c.c. 

2nd „ „ ... 12-5 „ 



Amount of indigo used . . .2*2 

1 c.c. of indigo = o'o86 milligrams of N 2 

.". 2*2 C.C. „ =0*1936 „ „ 



NITRATES AND NITRITES 23 

But this amount was contained in 20 c.c. of the water. 
.*. in 100 c.c. there will be 0*968 milligrams of N 2 
or 0*968 parts per 100,000 of the water. 

Notes 

It is common practice to standardize the indigo for the amount 
of water that is to be used. The same quantity should therefore 
always be used. 20 c.c. has been found to be convenient. 

If the nitrates are present in considerable amount, the solution 
becomes so dark that it is very difficult to determine the " end 
point " with accuracy. In these cases it becomes necessary to 
dilute the water, generally from 1 to 4 times. Very occasionally 
it becomes necessary to dilute 10 or even 20 times. If it is 
necessary to dilute 4 times, 10 c.c. should be thoroughly well 
mixed with 30 c.c. of distilled water, and 20 c.c. of the diluted 
water pipetted into the beaker and treated as in the case of the 
undiluted water. 

When 20 c.c. of the concentrated H 2 S0 4 are added, the right 
amount of heat is generated to allow the oxidation of the indigo 
by the liberated nitric acid. The estimation must therefore be 
done as quickly as possible. It is in order that this temperature 
may be maintained up to the end point that the second order of 
procedure given above is adopted. 

II. COPPER-ZINC COUPLE METHOD 
Apparatus, etc., required 

1. Zinc foil, about 9 sq. inches. 

2. 3% solution of CuS0 4 . 

3. Wide-mouthed, glass-stoppered bottle of about 8 oz. capacity. 

4. 100 c.c. graduated measuring-glass. 

5. 10 c.c. pipette. 

6. Apparatus as in the estimation of free and saline ammonia. 

The Process 

1. Immerse the zinc foil in the copper sulphate solution until the 

surface of the zinc is coated with metallic copper. 

2. Wash the foil in ammonia- free water. 

3. Place the foil in the glass-stoppered bottle. 

4. Put about 120 c.c. of the water to be examined into the bottle* 

5. Stopper tightly, and put the bottle away in a warm dark place 

until the following day. 



24 WATER ANALYSIS 

6. Then remove 10 c.c. of the water and test for the presence of 

nitrites by Griess's method. 

7. If nitrites are present, restopper the botfe, put it away again 

for 12 hours and then test again. 

8. If nitrites are absent, measure out 100 c.c. of the water, 

transfer it to a flask or retort, and estimate the ammonia in 
the ordinary way. 

From the amount of ammonia obtained, the nitrogen as nitrites 
and nitrates is readily calculated. 

It will be evident that by this process any ammonia which is 
present in the water originally, will be present after the conversion 
of the nitrates and nitrites into ammonia, and therefore the 
ammonia found will represent the ammonia reduced from the 
nitrates plus the original ammonia. The amount of original 
ammonia must be deducted in order to find the true amount of 
nitrates and nitrites. 

Explanation 

The zinc copper couple liberates nascent hydrogen from the 
water, and this reduces the nitrates and nitrites to ammonia. 

HNO3 + 8H = NH 3 + 3 H 2 
HN0 2 +6H = NH 3 + 2 H 2 



OXYGEN ABSORBED 

TIDY'S PROCESS 

Apparatus, etc., required 

1. Two glass-stoppered bottles holding about 350 c.c. 

2. A water bath or incubator regulated at 27 C. 

3. A 50 c.c. burette graduated in tenths of a c.c. 

4. Organically pure ammonia-free water. 

5. Thiosulphate solution. 

6. Starch solution. 

7. Potassium iodide solution. 

8. 25% sulphuric acid. 

9. Standard permanganate solution. 

The Process 

1. Measure 250 c.c. of good distilled water into one bottle (the 
control), and 250 c.c. of the water under examination into 
the other. 



TIDY'S PROCESS 25 

2. Into each of these measure 10 c.c. of the standard potassium 

permanganate solution and 10 c.c. of the specially prepared, 
organically pure 25% H 2 S0 4 . 

3. Shake the bottles up and place in the water bath at 27 C. for 

four hours. 

4. At the end of this time add a few drops of the KI solution 

to each bottle. The pink colour will disappear and be 
replaced by a yellow one. 

5. Fill the burette with thiosulphate solution, and carefully read 

the height of the fluid. 

6. Run the thiosulphate into the control bottle until the yellow 

colour is almost discharged and then add a few drops of 
starch solution. The colour will now turn blue. Add the 
thiosulphate cautiously until all the colour is discharged, and 
read off the height of the fluid in the burette. 

7. Repeat this with the bottle containing the sample of water. 

Explanation 

The potassium permanganate in the presence of sulphuric acid 
oxidizes the organic matter in the water. 

K 2 Mn 2 8 + 3H 2 S0 4 - K 2 S0 4 + 2 MnS0 4 + 3H 2 + 5O 

The amount of this organic matter is to a certain extent gauged 
by the quantity of permanganate used up. 

The control bottle, containing only distilled water and there- 
fore no organic matter, will use up no oxygen, and so will contain 
permanganate at the end of the four hours, the equivalent of 
1 milligram of oxygen. 

The potassium iodide is decomposed by the permanganate, 
and iodine is liberated. 
K 2 Mn 2 8 + 8H 2 S0 4 + 10KI = 6K 2 S0 4 + 2 MnS0 4 + 8H 2 + 5l 2 

The amount of iodine liberated will be in proportion to the 
amount of permanganate in solution (i.e. not used up). In this 
case it will be -the equivalent of 1 milligram of oxygen. 

The amount of iodine liberated is now measured by the 
quantity of thiosulphate required to decolourize the solution, 
which it does according to the following equation : — 
2Na 2 S 2 3 + 1 2 = 2NaI + Na 2 S 4 6 

The starch solution is added towards the end of the operation 
in order the more easily to determine the actual end point. It 
performs no other function. 



26 WATER ANALYSIS 

EXAMPLE 

Control (C) took 15*2 c.c. of the thiosulphate to decolourize 
the iodine. 

The sample of water took 13*4 c.c, to decolourize it. 

15*2 c.c. of thiosulphate therefore represent 10 c.c. of the per- 
manganate solution, and this equals 1 milligram of available 
oxygen. 

The sample of water required 13*4 c.c. The difference be- 
tween this and 15*2 c.c. represents the amount of oxygen absorbed 
by the water. This difference is i*8 c.c. 

Now as 15*2 c.c. of thiosulphate = 1 milligram of oxygen, 

1 "8 . . 

i*8 c.c. will be — — of 1 milligram, which equals 0*118 milli- 
grams. 

But 250 c.c. of the water was taken; therefore 100 c.c. will 
absorb 0*047 milligrams; or, in other words, the oxygen 
absorbed during four hours at 27 C. is equal to 0*047 parts per 
100,000. 

Notes 

The results obtained by this method merely give an indication 
as to whether or not there is much oxidizable organic matter in 
the water. Various analysts take various times and temperatures 
in performing this experiment. For examination purposes the 
student will find that three hours at room temperature will be 
the most convenient conditions under which to perform the 
experiment. 

One of the chief reasons for making a control examination for 
each sample tested, is that the solution of thiosulphate undergoes 
changes and gradually becomes weaker. The trouble of con- 
stantly having a standard solution, therefore, would be found in 
practice far greater than making a control each time. The 
purpose in allowing the control to stand along with the sample 
is to eliminate the possibilities of error due to the destruction 
of the permanganate by any condition other than the organic 
matter present in the sample. 

If, as sometimes happens with a bad water such as sewage, the 
10 c.c. of permanganate is totally decolourized before the expiry 
of the four hours, a further 10 c.c. should be added, and if 
necessary a third 10 c.c, and the amount of thiosulphate used 
to decolourize the iodine liberated deducted from twice or three 



POISONOUS METALS 27 

times that required to decolourize the control, in order to obtain 
the equivalent of oxygen absorbed, in terms of thiosulphate. 

This method of ascertaining the amount of organic matter 
present in a sample of water is useless in the presence of iron 
in the ferrous state, since this takes up the permanganate with 
great avidity. 

POISONOUS METALS 

A. LEAD 

1. Qualitative Tests 

a. With Sulphuretted Hydrogen 

Pipette about 100 c.c. of the water into a Nessler glass, add 
two or three drops of acetic acid, and then several drops of 
a saturated aqueous solution of H 2 S. Stir the mixture well. If 
there is an appreciable amount of lead in the water, there will be 
a brown colour developed directly. 

b. With Potassium Chromate 

If the H 2 S gives a decided colour with the sample of water, 
add a few drops of KCr0 4 to a fresh 100 c.c. If lead is present, 
a yellow precipitate will be formed. 

If only a very faint darkening is observed with the H 2 S it is 
necessary to concentrate the water. This is done by evaporating 
about 250 c.c. in an evaporating dish to 20 c.c. and then adding 
the KCr0 4 . By this means the precipitate is much more easily 
seen. 

c. With Sulphuric Acid 

Add a few drops of H 2 S0 4 to 100 c.c. of the water and allow 
it to stand for some time. A white precipitate of lead sulphate 
will be formed. 

2. Quantitative Estimation 

Having now determined that lead is present in the water, it 
remains to find the quantity. 

1. Measure 100 c.c. of the water into a Nessler glass, add a few 

drops of acetic acid and several drops of sulphuretted 
hydrogen. 

2. Run 100 c.c. of distilled water into another Nessler glass, add 

a few drops of acetic acid and several of sulphuretted 
hydrogen. 



28 WATER ANALYSIS 

3. Allow the standard solution of lead (1 c.c. = o*i milligram 

of Pb) to run into this, drop by drop, stirring constantly 
until the depth of colour is the same in both glasses. 

4. Read off the quantity of lead solution used, and calculate the 

quantity of lead in the sample. 

EXAMPLE 

100 c.c. of the water were found to contain as much lead as 
was present in 2 c.c. of the standard lead solution. 

1 c.c. = o*i milligrams of lead .*. 2 c.c. = 0*2 milligrams of lead 
But this was present in 100 c.c, i.e. there are 0*2 parts of 
lead in 100,000 of the water. 

Notes 

If a very small quantity of lead is present in the water, and it 
is necessary to know the exact amount, 250 or 500 c.c. of the 
water acidified with acetic acid should be evaporated almost to 
dryness. The residue should be poured on to a small filter- 
paper, and the dish and filter-paper washed well with small 
quantities of distilled water acidified with acetic acid. The 
washing should be collected in a Nessler glass and made up 
to 50 c.c. 

The determination is now proceeded with, and the quantity 
found will be that present in 250 c.c. of the original water. 

If copper is present as well as lead, the above method will 
estimate both these metals. The copper must be estimated 
separately, as will be seen later, and the amount thus obtained 
deducted from that obtained by the H 2 S method. 

The difference will be the quantity of lead. 

B. COPPER 

1. Qualitative Tests 

a. With Sulphuretted Hydrogen 

This test is performed in exactly the same manner as was 
described under lead. 

b. With Potassium Ferrocyanide 

1. Place about 100 c.c. of the water in a Nessler glass and 
acidulate with a little dilute hydrochloric acid. 



POISONOUS METALS 29 

2. Add a few drops of potassium ferrocyanide and stir up well. 
A brown or chocolate colour will be developed if copper is 
present, owing to the formation of copper ferrocyanide. 

c. By the Platinum-Steel Couple 
This is an extremely delicate test, and is very simple. 
Half fill a platinum dish with the water and acidulate with 
HC1. Then lay a large polished steel needle in the dish so that 
one end rests on the bottom, and the other on the edge. Part 
will thus be immersed and part dry. After being in this position 
for about half an hour the needle is withdrawn and examined. 
If copper is present in the water there will be a deposit on the 
needle. This deposit can be made more conspicuous, if neces- 
sary, by allowing it to come in contact with bromine vapour for a 
few seconds. 

2. Quantitative Estimation 
Having determined that copper is present, it remains to 
estimate the amount. 

1. Measure 100 c.c. of the water into a Nessler glass, add a few 

drops of dilute HC1, and then sufficient K 4 Fe(CN) 6 to 
produce the maximum colour. 

2. Measure 100 c.c. of distilled water into another Nessler glass, 

add the same quantities of HC1 and K 4 Fe(CN) 6 as were 
added to the sample. 

3. Allow the standard solution of copper to run into this drop 

by drop until the colours match. When this occurs, read off 
the quantity used, and calculate the amount of copper present 
per 100,000. 

Notes 
In testing for copper, controls should always be made in a 
similar manner to those described for the determination of the 
presence of lead. 

c. IRON 

1. Qualitative Tests 

a. With Ammonium Sulphide 
Take about 100 c.c. of the water in a Nessler glass, add a few 
drops of ammonia solution and also a few drops of solution of 
ammonium chloride. Now add about 2 c.c. of a solution of 
ammonium sulphide. If iron is present, there will be a brown 
colour developed. 



30 WATER ANALYSIS 

b. With Potassium Ferrocyanide and Ferricyanide 

To ioo c.c. of the water add a few drops of dilute HC1 and 
a few drops of K 4 Fe(CN) 6 and K 3 Fe(CN) 6 . If a blue colour 
develops, iron is present either as a ferrous or a ferric salt. 

c. With Potassium Sulphocyanide 
To about ioo c.c. of the water add a few drops of pure 
dilute HN0 3 an d a crystal of KCNS. If iron is present a red 
colour will be formed. 

2. Quantitative Estimation 

1. Measure 100 c.c. of the water into a Nessler glass, and add a 

few drops of nitric acid and a few drops of a solution of 
potassium ferrocyanide until the blue colour produced 
reaches the maximum. 

2. Measure 100 c.c. of distilled water into another Nessler glass, 

add a few drops of potassium ferrocyanide solution, and 
then add the standard ferric chloride solution until the blue 
colour developed matches that in the first glass. 

3. Measure the amount of standard iron solution used, and thus 

calculate the amount of iron present in the sample water. 

Another method is to use potassium sulphocyanide instead of 
the ferrocyanide as an indicator. 

D. ZINC 

1. Qualitative Tests 

a. With Ammonium Sulphide 

Take about 100 c.c. of the water in a Nessler glass, add a few 
drops of NH 4 HO, and also a few drops of NH 4 C1 solution. Now 
add about 2 c.c. of a solution of fresh (NH 4 ) 2 S. If zinc is 
present in any but the minutest traces, a white precipitate of zinc 
sulphide will be produced. 

b. With Potassium Ferrocya?iide 

Acidulate 100 c.c. of the water with a few drops of HC1 and 
add a few drops of K 4 Fe(CN) 6 . If zinc is present in any but 
the smallest traces, a white precipitate will be formed. 

If the presence of zinc is suspected, and no precipitate is 



POISONOUS METALS 31 

obtained with either of the above reagents, half a litre of the 
water should be evaporated to a small bulk and tested in the 
above manner. 

2. Quantitative Estimation 

1. Having determined that neither lead nor copper is present in 

the water, measure 250 c.c. into an evaporating basin and 
evaporate over the water bath until the bulk is about 50 c.c. 

2. Add solution of NH 4 HO and filter any precipitated hydrated 

oxide of iron. To the filtrate add (NH 4 ) 2 S in slight excess. 

3. Filter the water through an ashless filter-paper, and wash the 

precipitate with dilute (NH 4 ) 2 S solution. 

4. Dry the precipitate in the water oven, transfer it together 

with the filter-paper to a tared porcelain crucible, and care- 
fully ignite over a Bunsen burner. 

5. Allow it to cool, and reweigh. The gain in weight represents 

the weight of oxide of zinc, and from this the amount of zinc 
present is calculated. 

Notes on Poisonous Metals in Drinking Waters 

Copper and zinc are rarely found in drinking waters, and 
when they are present they are derived from copper and zinc 
storage vessels. Iron is present naturally in some waters, 
especially in those collected from the greensand strata. Lead, 
the metal occurring most frequently in waters, is derived from the 
action of the water on the lead pipes through which the supply 
is distributed to the consumers. 

The kinds of water which have a marked solvent action on 
lead are : — 

1. Soft waters. 

2. Waters not aerated. 

3. Waters containing excess of nitrate. 

4. Acid waters as from peaty soils. 

From the hygienic point of view, the presence of lead in water 
is one of very great importance, and therefore the estimation of 
the lead when it is present, or even the detection of the lead, is a 
very important point. The consumption of water containing 
lead gives rise, as is well known, to symptoms of chronic lead- 
poisoning, and it is laid down by many authorities that not more 
than ^th grain per gallon (0-025 parts per 100,000) should ever 
be present in a water intended for human consumption. Other 



32 WATER ANALYSIS 

authorities who are not quite so rigid lay down that ^th grain is 
the limit, but it follows from what has been said above that when 
two sources of water are available, that which contains no lead, 
or will take up no lead from the pipes, should always be chosen 
in preference to one which would take up lead. 



GASES IN WATER 

The detection and estimation of the gases contained in various 
samples of water are interesting, but are of questionable hygienic 
import. One gas is, however, of some importance, namely 
oxygen, and a brief account of the estimation will be given. 
Should the reader require to estimate other gases, he can find all 
the details in several text-books more pretentious than this. 

OXYGEN IN WATER 

WINKLER'S METHOD 

Apparatus, etc., required 

i. Two glass-stoppered bottles of 350 c.c. capacity. 

2. Solution of MnCl 2 (40 grammes to 100 c.c). 

3. Solution of KOH (33%) and KI (10%) in water. 

4. 100 c.c. burette, graduated in o'i c.c. 

5. Freshly prepared starch solution. 

6. Sodium thiosulphate solution (1 c.c. = 0*25 milligrams of 

oxygen). 

7. Two large porcelain dishes. 

8. Pure H 2 S0 4 . 

The Process 

1. Fill one of the bottles with distilled water, shaking it well so 

that as much oxygen as possible shall be dissolved. 

2. Fill the other bottle by means of a syphon with the water 

under examination. Do not splash the water or shake 
the bottle. 

3. To each bottle add 1 c.c. of the strong solution of 

manganous chloride. 

4. To each bottle add 2 c.c. of the solution containing KOH 

and KI. 

5. Replace the stoppers, taking care that each bottle is quite 

full and no air bubbles are included. 



DISSOLVED OXYGEN 33 

6. Invert both bottles several times, so as to mix the solutions 

in them. 

7. Put the bottles away in a dark cupboard for fifteen minutes. 

8. Remove the bottles from the cupboard, and pour their con- 

tents carefully, and without splashing, into the two porce- 
lain dishes. 

9. Label the dishes. 

10. To each dish add 3 c.c. of H 2 S0 4 . The brown colour that 

appears is due to free iodine. 
n. From the burette run into the dishes enough of the thiosul- 

phate solution to discharge the brown colour. Use the 

starch solution, as in Tidy's process, to estimate the end 

point. 
12. Read the burette, and note the amounts of thiosulphate 

solution used in both the dishes. 

The Explanation 

The MnCl 2 with the KOH forms manganous hydrate : — 

MnCl 2 + 2KOH = 2KCI + Mn(OH) 2 
And when this Mn(OH) 2 is in contact with water containing 
dissolved oxygen, it takes up the oxygen and is oxidized to 
manganic hydrate : — 

4 Mn(OH) 2 + 2H 2 + 2 = 4 Mn(OH) 3 
The amount of Mn(OH) 3 formed is an index, therefore, of the 
amount of dissolved oxygen in the water. 

On addition of H 2 S0 4 , the Mn(OH) 3 is converted into 
manganic sulphate, which latter reacts with the KI and liberates 
free iodine. 

2 Mn(OH) 3 + 3H 2 S0 4 = Mn 2 (S0 4 ) 3 + 6H 2 
and Mn 2 (S0 4 ) 3 + 2 KI = 2 MnS0 4 + K 2 S0 4 + 1 2 
The amount of iodine liberated is proportionate to the amount 
of Mn 2 (S0 4 ) 3 , and so proportionate to the amount of Mn(OH) 3 , 
and to the oxygen dissolved in the water. 

EXAMPLE 

The dish containing the distilled water shaken with air was 
found to require 14*4 c.c. of sodium thiosulphate solution, in 
order that the colour of the iodine might be discharged. 
Now 1 c.c. of thiosulphate solution = 0*25 milligrams of oxygen 
.'. x 4'4 » n = 3' 6 ° » m 

3 



34 WATER ANALYSIS 

.". in 350 c.c. of distilled water there were 3*6 milligrams of 

oxygen 
.'. in 100 c.c. of distilled water there were 1*02 milligrams of 

oxygen 
or 1*02 parts of oxygen per 100,000 of the water. 

Again, it was found that the dish containing the water under 
examination required 12*6 c.c. of sodium thiosulphate solution, 
in order that the brown colour of the iodine might be dis- 
charged. 

And since 1 c.c. of thiosulphate solution = 0.2 5 milligrams of 
oxygen 
.*. 12*6 c.c. of thiosulphate solution = 3*15 milligrams of oxygen 
.*. in 350 c.c. of the sample water there were 3 '15 milligrams of 

oxygen 
,\ in 100 c c. of the sample water there were 0*90 milligrams of 
oxygen 
or 0*9 parts of oxygen per 100,000 of the water. 

But we have seen that a fully saturated water takes up 1*02 
parts of oxygen; and if this represents 100 per cent, then the 
water under consideration will give a percentage saturation with 

r O'O X IOO on 0/ 

oxygen of — = 88*2%. 

1*02 

The result may be returned either as a percentage or in terms 
of the actual amount of oxygen present in the water. Both 
results are given in this example. 

Notes 

The estimation of the amount of oxygen dissolved in water is 
of some value, as the oxygen becomes much diminished in the 
presence of organic matter. A low figure for dissolved oxygen is, 
at least, confirmatory evidence in condemning a water of which 
suspicion is entertained. 

When decolourizing with thiosulphate solution, it often 
happens that the colour returns two or three times. The estima- 
tion, therefore, should not be considered as completed until the 
water remains colourless for four or five minutes. 

Although the thiosulphate is made up to a definite strength, it 
will not keep constant ; so it is advisable to standardize it occa- 
sionally against standard potassium permanganate. 



INTERPRETATION OF RESULTS 35 

THE INTERPRETATION OF AN ANALYSIS OF WATER 

The attention of the Public Health Student is especially 
directed to the importance of grasping the fundamental prin- 
ciples laid down in this chapter; and he is asked to give very 
careful attention to the analyses of various waters, with which the 
lessons of this chapter are illustrated. 

Every water sample must be treated on its own merits, and 
local circumstances and the history of the water must be taken 
into consideration before the analyst gives a favourable or an 
adverse judgment. It is easy to say when a water is good ; 
equally easy to determine when it is very bad ; but often ex- 
tremely difficult to decide on many waters which are neither 
excellent nor foul. It is in judgment on these indifferent waters 
that a student will be most troubled ; and it is here that some 
knowledge of geology, and of the composition of waters from 
various strata, will be of use to him in deciding whether or not 
the sample under his consideration deviates from the type to 
which it should conform. 

In the first place it must be remembered that no water must 
be passed or condemned, unless it contain poisonous doses of 
lead or copper, on any single figure in the analysis. All the 
figures must be taken together ; this will be seen by the follow- 
ing notes upon the individual estimations. 

Physical Characters 

Almost all waters used for drinking purposes have excellent 
physical characters. The colour is faintly blue as seen in the 
two-foot tube, the water is bright and free from opacity, and has 
no smell nor taste. Any odour or opacity should at once arouse 
suspicion about the sample. If the water is brown in colour this 
may be due to salts of iron, or to the colouring matter extracted 
by the water from peat and upland surfaces. There should be 
no sediment, or very little, and in a good water this sediment 
should contain neither epithelium nor hairs nor matter of obvious 
animal origin. 

Total Solids 

These vary very much in different samples of water. Rain 
water may have about 3 parts per 100,000 of total solids, 
and a water derived from the greensand as much as no parts 
per 100,000. A well, polluted by sea water, may, of course, 



36 WATER ANALYSIS 

show still higher figures. Generally speaking, a good drinking 
water should not contain more than ioo parts per 100,000 of 
total solids. 

On ignition some of these total solids are removed, and the 
proportion removed is of some importance. Salts, except for 
their water of crystallization, are not affected by ignition ; but 
organic matter present is driven off. If, therefore, there is much 
loss on ignition, and if the residue shows signs of blackening, the 
sample should be regarded as suspicious. 

REACTION OF THE WATER 

Most drinking waters are alkaline. Some, however, derived 
from upland surfaces, may be acid, and even markedly so. Now 
an acid water will dissolve lead pipes and take lead into solution, 
greatly to the detriment of the consumer : so, if a water is acid, 
search should be made for lead, and the water condemned if this 
is found in any amount exceeding 0*025 parts per 100,000. In 
itself, and without the lead, an acid water is of no harm. 

HARDNESS 

The hardness of a water is not of very great hygienic import- 
ance. It is maintained by many medical men that water which 
is excessively hard, say above 30 parts per 100,000, causes a 
certain amount of dyspepsia, and a water containing such a 
degree of hardness could not be recommended for drinking pur- 
poses. The chief objection to having a hard water is a purely 
economical one. It is said that since Glasgow has been supplied 
with water from Loch Katrine the saving to the city of Glasgow 
in soap per annum has been about ^30,000. Speaking generally, 
the hardest waters are those which are derived from superficial 
wells. The softest is of course pure rain water. The average 
hardness of the London water is about 16 parts per 100,000, and 
this is looked upon generally as the limit of hardness for a water 
for drinking purposes. 

CHLORIDES 

The sources of chlorides in water are various. Rain water, 
especially when collected near the sea, always contains traces of 
salt. Certain geological formations also contain considerable 
quantities of chlorides. This being so, the purest water would 
be expected to contain certain traces of chlorides, and this is 
found to be invariably the case. The water drawn from districts 



INTERPRETATION OF RESULTS 37 

in which there are manufactories, such as alkali works, mines, 
etc., is also found to be rich in chlorine. Urine contains about 
i% of chlorides, and therefore the addition of sewage to any 
drinking water would probably raise the quantity of chlorine. 
In considering the percentage of chloride which is to be allowed, 
it is necessary in the first place to know something about the 
geological stratum from which the water is drawn. 

If the chlorine content of a water is found to be uniform 
throughout the year, any deviation from the usual figure may well 
give rise to suspicion that the water has been contaminated. 
Well waters from the chalk and limestone generally have a 
chlorine figure not over 3 parts per 100,000; from the greensand 
and some of the marls, and in the neighbourhood of salt mines 
or the sea, the chlorine figure may be very high. Rain water 
collected in or near towns contains more chlorine than that 
collected in the open country. 

FREE AND SALINE AMMONIA 

Waters from all sources contain ammonia. Even rain water 
from the country shows some traces. Many very pure waters 
from deep wells have large quantities of ammonia, which is 
derived from the reduction of nitrates and nitrites : the green- 
sand waters are examples of this. Speaking generally, free and 
saline ammonia should not exceed 0*005 parts per 100,000. If 
it exceeds this, the albuminoid ammonia figure should be low. 
Water which is derived from rivers, sewage, or known polluted 
sources contains large quantities of ammonia. 

ALBUMINOID AMMONIA 

It will be understood from what has been said in the sections 
on the actual analysis of water that the albuminoid ammonia 
does not exist as such in the water, but is simply a laboratory 
product from the organic matter present in the water. From this 
it will be seen that even where albuminoid ammonia exists in 
considerable quantities, there is no method of determining 
whether the organic material present in the water is derived from 
vegetable or animal sources. Nor is the amount of albuminoid 
ammonia found in the water a very accurate test of the amount 
of organic material present in the water. Waters which are 
derived from deep wells, or even from surface wells where there 
is no possibility of contamination, do not, however, yield much 
albuminoid ammonia. Indeed, many deep well waters, that is 



38 WATER ANALYSIS 

waters derived from beneath the impervious layers, contain prac- 
tically no albuminoid ammonia at all. The consideration, 
however, of the quantities of free ammonia and albuminoid 
ammonia together, often gives a good clue to the presence or no 
of contamination. 

As a rule the figure for albuminoid ammonia should not 
exceed 0*005 parts per 100,000. If it exceeds this, the figure for 
free and saline ammonia should be low. In other words, the free 
ammonia and the albuminoid ammonia should not both be high 
in a water; if the one is raised, the other should not also exceed 
the standard. 

The albuminoid ammonia figure is high in waters that have 
been polluted with animal matter ; and is also raised in upland 
surface waters, in which latter case the free ammonia figure is 
invariably low. 

NITRITES 

Nitrites may be found in waters that have been polluted by 
sewage or excrement. Lower greensand waters also may contain 
nitrites from the reduction of nitrates by the ferrous salts of the 
stratum. Unless it can be shown that nitrites are present in 
a drinking water in consequence of such reduction of nitrates, the 
water, if it contains even traces of any nitrites, must be considered 
as highly suspicious. 

NITRATES 

Nitrates may be regarded as one of the end products of the 
oxidation of organic matter, and their presence in water is there- 
fore an index of past organic contamination. Certainly, the 
organic contamination may be very remote, and the nitrate may 
have been produced many years before the water comes to be 
analysed. If the other figures of the analysis are good, and the 
nitrate figure is high, this excess over the average may be 
accounted for by the nitrates in the stratum, and is of little con- 
sequence ; but if the rest of the analysis throws doubt upon the 
water, a raised nitrate figure (together, possibly, with increased 
chlorine) will turn the balance against the water under considera- 
tion. Some geological strata contain nitrates in considerable 
degree, but a large proportion of nitrates is by no means so 
common as in the case of chlorine. Peaty upland waters and 
waters derived from the Liassic strata may be rich in nitrates ; 
but, speaking as a rule, to which, of course, there are notable 
exceptions, a good drinking water ought not to contain more 
than o'5 parts per 100,000 of nitric nitrogen. 



INTERPRETATION OF RESULTS 



39 



Oxygen Absorbed from Permanganate 

Waters which contain a considerable amount of organic 
material absorb an amount of oxygen which to some degree 
corresponds to the organic material present. Organic material 
animal in origin absorbs oxygen more readily than does that 
derived from vegetable sources. If this were all, the oxygen 
process would be an extremely valuable one, but unfortunately 
this is not the case. Certain other matters, particularly the proto- 
salts of iron, etc., will absorb oxygen when in a water containing 
absolutely no organic material. If, therefore, any of these salts 
are present, a considerable allowance must be made for the 
amount of oxygen absorbed, and if in the water any sediment is 
present which consists of these, the water must be carefully 
filtered before being submitted to the process. 

Frankland and Tidy give the following table, which may be 
useful as forming some standard to which waters should comply 
in regard to the oxygen absorbed. 

Amounts of Oxygen Absorbed by 100,000 Parts of Water 





Water from Upland 
Surfaces. 


Water from Sources 

other than Upland 

Surfaces. 


Water of great organic 

purity 
Water of medium purity 
Water of double purity 
Polluted water 


Not more than o*i 

>i >, 0*4 

More than 0*4 


Not more than 0*05 
015 

More than 0*2 



Examples of Waters from various Sources 

The first two analyses given are those of a very good and a very 
bad water respectively ; the remainder are analyses of waters from 
different sources and from some of the main water-bearing 
geological strata in this country. 

Analyses 3-16 inclusive show uncontaminated waters; 17-22 
show some river water analyses; and 23-30 are analyses of 
waters that are contaminated. In the light of what has already 
been said in this chapter, the careful consideration of these 



4 o WATER ANALYSIS 

various analyses should do much to help the student to 
appreciate the significance of the analytical figures. 





No. 1 


No. 2 




A very good water. 


A very bad water. 


Physical characters 


Excellent 


Excellent 


Reaction 


Slightly alkaline 


Very alkaline 


Total solids . 


i6'4 


42-8 


Volatile . 


3* 


20-3 


Appearance on igni- 






tion 


Nil 


Marked blackening 


Hardness 


9-2 


3° 


Chlorine 


i'3 


6-2 


Free and saline ammonia 


*ooo8 


0*030 


Albuminoid ammonia . 


O'OOI 


018 


Nitrites 


Nil 


A trace 


Nitrates 


O'OI 


0*96 


Oxygen absorbed in 4 






hours at 27 C. . 


O'OI 


o'34 



Notes on i and 2 

All figures represent parts per 100,000. These two waters are 
good examples of the extremes of which it is easy to judge. 





No. 3 


No. 4 




Rain water — country. 


Rain water — town. 


Physical characters 


Excellent 


Good 


Reaction 


Faintly alkaline 


Slightly acid 


Total Solids . 


3-2 


5' 1 


Volatile . 


17 


27 


Appearance on igni- 






tion 


Nil 


Nil 


Hardness 


°'5 


07 


Chlorine 


0*31 


1*2 


Free and saline ammonia 


0*042 


0'058 


Albuminoid ammonia . 


0*003 


0'005 


Nitrites 


Nil 


Nil 


Nitrates 


O'OI 


0*04 


Oxygen absorbed in 4 






hours at 27 C. . 


0*004 


022 



INTERPRETATION OF RESULTS 



4i 



Notes on 3 and 4 

Both these waters show the low total solids and the low figure 
for hardness characteristic of rain water. The free ammonia 
figure is high in each; but the albuminoid ammonia and the 
oxygen absorbed are low, showing the freedom of these waters 
from much organic matter. Obviously, No. 3 is a better water 
than No. 4. 





No. 5 


No. 6 




Upland surface water, not 


Upland surface water, 




peaty. 


peaty. 


Physical characters 


Good 


Brown 


Reaction 


Neutral 


Acid 


Total solids . 


5'° 


10 *o 


Volatile . 


i'7 


7'6 


Appearance on igni- 






tion 


Nil 


Blackening 


Hardness 


29 


3*4 


Chlorine 


0-9 


0-9 


Free and saline ammonia 


0-003 


O'OOI 


Albuminoid ammonia . 


0*004 


0'020 


Nitrites 


Nil 


Nil 


Nitrates 


o'o6 


0*04 


Oxygen absorbed at 27 






C. in 4 hours 


• 0-05 


0T4 



Notes on 5 and 6 

Both these waters show low figures for hardness and for total 
solids, although No. 6 gives slightly higher readings in these 
respects than No. 5. No. 5 really is very much like the rain 
water analyses shown, except that the ammonia figure is less. 
No. 6 is typical of peaty waters, being acid and having a high 
figure for volatile solids : these latter it is noticed show charring 
on ignition, and are composed of organic matter derived from 
the peat. The high figure for albuminoid ammonia is due to 
this vegetable organic matter. Note that in No. 6 the figure for 
free ammonia is low. Both waters were free from contamination 
with animal organic matter. 



42 



WATER ANALYSIS 





No. 7 


No. 8 




Subsoil water. Shallow 


Subsoil water. Shallow 




well in Sand. 


well in Gravel. 


Physical characters 


Excellent 


Excellent 


Reaction 


Alkaline 


Alkaline 


Total solids . 


8- 5 


32-2 


Volatile 


27 


IOI 


Appearance on ignition 


Nil 


Nil 


Hardness 


57 


25*5 


Chlorine 


20 


2'0 


Free and saline ammonia 


Trace 


Trace 


Albuminoid ammonia . 


0*005 


0*0005 


Nitrites 


Nil 


Nil 


Nitrates 


O'OI 


C51 


Oxygen absorbed at 27°C. 






in 4 hours 


0*07 


001 



Notes on 7 and 8 

Both these are very good waters. They show low ammonia 
figures, and low figures for the oxygen absorbed from perman- 
ganate. No. 7 does not show so much hardness as most shallow 
well waters ; No. 8, however, is very hard. The nitrate figure of 
No. 8 is high, but of little import since the water is, in other 
respects, so excellent : probably these nitrates are from some very 
old organic pollution of the gravel from which the water was drawn. 
Shallow well waters are not usually so pure as these, and have 
frequently much larger quantities of ammonia, both free and 
albuminoid. 





No. 9 


No. 10 




Deep well in the Chalk. 
Excellent 


Deep well in the Chalk. 


Physical characters 


Excellent 


Reaction 


Alkaline 


Alkaline 


Total solids . 


26*5 


357 


Volatile 


9-0 


10*4 


Appearance on ignition 


Nil 


Nil 


Hardness 


20 *4 


21*6 


Chlorine 


1 '5 


17 


Free and saline ammonia 


0*0005 


0*0015 


Albuminoid ammonia . 


0*0005 


O'COI 


Nitrites 


Nil 


Nil 


Nitrates 


0*41 


0*27 


Oxygen absorbed in 4 






hours at 27 C. 


O'OI 


0*03 



INTERPRETATION OF RESULTS 



43 



Notes on 9 and 10 

Both of these are excellent chalk waters in which the hardness 
is fairly high : about half this hardness is temporary and can be 
removed by appropriate softening processes. The chlorides and 
nitrates are, of course, derived from the strata through which the 
water has passed. The ammonia figures and the oxygen absorbed 
are low. Some chalk waters contain much more total solids 
than do these. 





No. 11 


No. 12 




Upper Grcensand. 


Lower Greensand. 


Physical characters 


Excellent 


Good 


Reaction 


Alkaline 


Alkaline 


Total solids 


131 


1060 


Volatile 


3*o 


21-4 


Appearance on igni- 






tion 


Nil 


Nil 


Hardness 


5-8 


18-0 


Chlorine 


2'0 


117 


Freeandsaline ammonia 


Trace 


0-038 


Albuminoid ammonia . 


O'OOI 


O'OOI 


Nitrites 


. Nil 


Trace 


Nitrates 


0*25 


0*30 


Oxygen absorbed at 






27 C. in 4 hours 


Nil 


0*36 



Notes on 11 and 12 

No. 1 1 is obviously an excellent water, and otherwise has no 
special characteristics. No. 12, at first sight, might seem to be 
much polluted : the free ammonia figure is high, and the chlorides 
are excessive, moreover nitrates are present. This water on 
analysis showed a trace of iron, and to the reducing properties of 
this metal the figures on which I have commented are due. The 
nitrites are formed by the reduction of nitrates, and so is the 
free ammonia : the high chlorine figure is typical of some green- 
sand waters. Note the small amount of albuminoid ammonia, 
which points to the absence of organic pollution. 



44 



WATER ANALYSIS 





No. 13 


No. 14 




Oolite. 


New Red Sandstone. 


Physical characters 


Excellent 


Excellent 


Reaction 


Alkaline 


Alkaline 


Total solids 


74*6 


33*5 


Volatile . 


18-2 


9-1 


Appearance on igni- 






tion 


Nil 


Nil 


Hardness 


27 


22*8 


Chlorine 


2*2 


2-8 


Freeand saline ammonia 


0*0004 


Trace 


Albuminoid ammonia . 


Trace 


Trace 


Nitrites 


Nil 


Nil 


Nitrates 


O'OI 


0*25 


Oxygen absorbed at 






27 C. in 4 hours 


0008 


Nil 



Notes on 13 and 14 

Both these are very good waters. No. 13 from the Oolite is 
very similar in composition to a chalk water. No. 14 is better 
than most sandstone waters : these vary greatly in their com- 
position, depending on the nature of red sandstone deposit, 
which may be pure or impure, soft or hard. The total solids 
and hardness in these waters may in consequence be sometimes 
very high. 





No. 15 


No. 16 




Coal Measures. 


Carboniferous Limestone. 


Physical characters 


Excellent 


Excellent 


Reaction 


Alkaline 


Alkaline 


Total solids . 


55'9 


30 '4 


Volatile . 


147 


87 


Appearance on igni- 






tion 


Nil 


Nil 


Hardness 


357 


23 


Chlorine 


I '2 


17 


Freeand saline ammonia 


0*006 


0*002 


Albuminoid ammonia . 


0*002 


O'OOI 


Nitrites 


Nil 


Nil 


Nitrates 


0*004 


0*27 


Oxygen absorbed at 






27 C. in 4 hours 


0*4 


0*056 



INTERPRETATION OF RESULTS 



45 



Notes on 15 and 16 

Both these waters are of good quality, as far as absence of 
organic pollution is concerned. No. 15 is exceptionally hard, 
and for that reason would make the water unfitted for trade 
purposes, unless some softening process were adopted. 

River Waters 

River waters may be divided into two classes — (a) those 
affected by the tide and (b) those not so affected. 

The first class will obviously show the variations of the second 
class, but will have an additional variant in the greater or less 
amount of sea water they contain at any moment. 

The non-tidal river waters will vary with the sources from 
which they are derived. In the upper reaches the rivulets may 
consist of either upland surface, subsoil or deep well water, the 
two latter appearing as springs. In their lower reaches most 
probably all rivers consist of a mixture of all three, in different 
proportions in different rivers. All rivers drain the subsoil water 
of their basins. 

In the following table these differences are well seen : — 







RIVER WATERS 














Parts per ioo 3 ooo 
















13 








c/5 






X 








No. 


Source. 


S 


c 
■a 




X 


IS 

"0 






O 
.P 

< 







m 


X 


.2 



V 


3 






c 
































J3 
















H 


H 


V 


in 


< 


£ 


£ 





17 


Scotland . 


4'i 


2 "4 


I'O 


Trace 


•005 


Nil 


Nil 


•18 


18 


Westmorland 


4*3 


2 -4 


I'O 


•008 


•01 s 


Nil 


Trace 


•15 


iq 


Devon 


S'o 


27 


ri 


Trace 


•005 


Nil 


Trace 


•05 


20 


Worcester . 


2VI 


II'O 


S-8 


•013 


•022 


Nil 


•07 


•44 


21 


Wilts 


54*5 


38-8 


2*4 


Trace 


•076 


Nil 


Trace 


•13 


22 


»> • • 


70-2 


51-4 


2*2 


•004 


•01 


Nil 


•09 


•14 



Notes on 17-22 

No. 17 is a pure water. No. 18 shows evidence of organic 
contamination, which is possibly vegetable in origin. No. 19 
is a pure water. No. 20 is very foul. Nos. 21 and 22 show 
much hardness, and high figures for the albuminoid ammonia. 



4 6 



WATER ANALYSIS 



The following eight analyses are those of contaminated 
waters : — 





No. 23 


No. 24 




Upland surface, peaty 
water. 


Shallow well- 
Sand. 


Physical characters 


Brown 


Excellent 


Reaction 


Acid 


Alkaline 


Total solids . 


162 


13-1 


Volatile . 


12*1 


8'2 


Appearance on igni- 
tion 
Hardness 


Blackening 

2-8 


Slight blackening 
SO 


Chlorine 


1 '5 


2*2 


Free and saline ammonia 


0*008 


0'0I3 


Albuminoid ammonia . 


0*026 


0*033 


Nitrites 


Nil 


Nil 


Nitrates 

Oxygen absorbed at 
27 C.jin 4 hours 


o*35 
0*46 


o*47 
053 



Notes on 23 and 24 

Both these waters are bad. Each shows high ammonia figures, 
increased nitrates and an excessive amount of oxygen absorbed 
from permanganate. Moreover, No. 23 shows a chlorine figure 
that is considerably above what is usually found in upland surface 
waters. Note that both these waters show some blackening 
when their total solids are ignited. 





No. 25 


No. 26 




Shallow well in gravel. 


Shallow well in gravel. 


Physical characters 


Slightly turbid 


Excellent 


Reaction 


Alkaline 


Alkaline 


Total solids 


24-6 


467 


Volatile . 


io*6 


1 6*9 


Appearance on igni- 






tion 


Marked blackening 


Nil 


Hardness 


13 6 


28-5 


Chlorine 


27 


5*9 


Freeand saline ammonia 


O'OIO 


O'OOI 


Albuminoid ammonia . 


0*022 


0*002 


Nitrites 


Nil 


Nil 


Nitrates 


0*91 


1*95 


Oxygen absorbed at 






27 C. in 4 hours 


0*20 


o*i8 



INTERPRETATION OF RESULTS 



47 



Notes on 25 and 26 

No. 25 is an analysis of a badly contaminated water, as shown by 
the blackening of the total solids on ignition and by the raised 
figures for the ammonia and nitrates. No. 26 shows an analysis 
of a well water that has been heavily polluted in the past ; but 
which has oxidized almost all the organic matter into nitrates. 
The chlorine figure for this well is also high, and the nitrates, of 
course, excessive. This water is potentially very dangerous : it 
was badly contaminated once, and there is no reason why this 
should not happen again. 





No. 27 


No. 28 




Shallow well in Chalk. 


Deep well in Chalk. 


Physical characters 


Excellent 


Excellent 


Reaction 


Alkaline 


Alkaline 


Total solids . 


60 *o 


72-8 


Volatile . 


22"I 


26*4 


Appearance on igni- 






tion 


Slight blackening 


Nil 


Hardness 


2 3'4 


200 


Chlorine 


2'8 


2'I 


Free and salineammonia 


0*007 


o'oo6 


Albuminoid ammonia . 


o # oo8 


0-005 


Nitrites 


Nil 


Nil 


Nitrates 


0*84 


0-52 


Oxygen absorbed at 






27 C. in 4 hours 


0*093 


0-07 



Notes on 27 and 28 

The shallow well water, No. 27, shows increased ammonia 
figures and high nitrates. The well was near a heap of manure, 
and water percolated from this through the subsoil and so into 
the well, the sides of which were not protected. No. 28 shows 
the analysis of a deep well chalk water, which was liable to inter- 
mittent contamination through defects in the stratum. Although 
the figures for No. 28 are not in themselves very excessive, they 
are greatly above the average for this well, in the waters of which 
albuminoid ammonia usually occurs only as a trace. The normal 
chlorine figure for this well is 1 *8. 



4 8 



WATER ANALYSIS 





No. 29 


No. 30 




Deep well in Chalk. 


Deep well in Chalk. 


Physical characters 


Excellent 


Brackish taste 


Reaction 


Alkaline 


Alkaline 


Total solids . 


40-4 


272*4 


Volatile . 


127 


36-0 


Appearance on igni- 






tion 


Faint blackening 


Faint blackening 


Hardness 


20-5 


50 


Chlorine 


17 


1 20 '4 


Free and saline ammonia 


0'002 


0*005 


Albuminoid ammonia . 


0-003 


0'002 


Nitrites 


Nil 


Nil 


Nitrates 


0-32 


1*07 


Oxygen absorbed at 






27 C. in 4 hours 


0-05 


0*071 



Notes on 29 and 30 

No. 29 looks like the analysis of a good water. Normally, 
however, the chlorine content of this water is 1*5, and the 
nitrate figure 0*22. Usually there are only traces of albuminoid 
ammonia, the saline ammonia is less than 0*001, and no oxygen 
is absorbed from permanganate. With the knowledge of this 
past history, we can condemn water No. 29 as showing organic 
contamination. The analysis No. 30 is of a deep well water near 
a tidal river. In times of flood and high tides some of the salt 
water finds its way into the well, as is shown by the analysis. 

In an examination, or where the student is required quickly 
to complete a water analysis, it is satisfactory to have a plan of 
work, and to adhere rigorously to this ; by so doing, labour is 
saved and the worker is spared from having to improvise on a 
sudden some scheme of his own. 

The following order of performing the various analyses of a 
water sample can be recommended : it is put forward as a useful 
scheme, but not necessarily the best. Whether the student 
adopts this or some other, let him adhere to one only ; for by so 
doing he will save himself much confusion, and be able the 
better to co-ordinate his work. 

1. Examine the physical properties of the water. Start the 
water evaporating for the estimation of the total solids ; start 
some more boiling for the estimation of permanent hardness. 



A SCHEME OF PRACTICAL WORK 49 

Set up and start the apparatus for estimating free and saline 
ammonia. Set some water boiling to concentrate for testing for 
poisonous metals. Start Tidy's process. 

2. Test for nitrites and nitrates. 

3. If nitrates are present start the phenol-sulphonic acid 
method of their estimation. 

Note 

All the lengthy processes have now been begun. The student 
can now perform various smaller manipulations until the free 
ammonia begins to come over. 

4. Estimate the chlorine. Estimate the nitrites, if such are 
present. Estimate the total hardness. Using the water that has 
been boiling, estimate the permanent hardness. Calculate the 
temporary hardness, and make notes of all your results. 

5. The free and saline ammonia should have distilled over by 
now. Start the distillation of the albuminoid ammonia. 

6. Estimate the free and saline ammonia. 

7. The phenol-sulphonic acid method should now be ready 
for completion. Finish this. 

8. Test the concentrated water for the poisonous metals. If 
present, estimate them. 

9. The albuminoid ammonia will now be distilled off. 
Estimate it. 

10. Weigh the total solids. Ignite and weigh the residue of 
non-volatile solids. 

n. Finish off Tidy's method. 

Note 

The wise student takes to examinations with him porcelain or 
platinum dishes of known weight. By so doing he saves much 
time and trouble. All results should be noted as they are 
obtained, and the last hour of the examination should be devoted 
to careful revision of the results and to the writing of the report. 

In all practical examinations it is impossible to over-estimate the 
importance of the written part, for it is by this, very largely, that 
the examiner judges of the candidate's grasp of the practical 
work. In the case of a water examination, the report should be 
written and arranged as if it were issued from the laboratory of a 
public analyst, and should be headed after the following 
manner : " Report on sample of water marked X, received on 



50 SEWAGE ANALYSIS 

such a date and examined on such a date." Then should follow 
details of the source of the water, if this is known. 

Workers in laboratories should aim at order and cleanliness in 
their methods. A messy and untidy bench does not impress an 
examiner favourably. 



SEWAGE ANALYSIS 

The composition of sewage varies within wide limits. Some 
towns have abundance of water to dilute their sewage ; others 
have little ; others, again, discharge trade refuse of every con- 
ceivable description into the sewers. There is no such thing as 
a standard sewage, for no two are alike. Even in one town or 
village the sewage varies in composition from day to day and 
from hour to hour. 

In making a chemical analysis of sewage, the procedure 
described under water is adopted, but with slight modifications. 

TOTAL SOLIDS 

These may be estimated in two ways. The total solids both in 
suspension and solution may be estimated, or a portion of the 
sewage may be filtered. The residue is dried, weighed, and sub- 
sequently ignited, and the loss on ignition noted; the filtrate is 
then evaporated to dryness, dried, weighed, and subsequently 
ignited and weighed again. 

Chlorides 

The chlorides of a sewage will be found to vary considerably. 
They are estimated in the way already described. 

Saline Ammonia 

As this is usually very high, often as high as i to 2 parts per 
100,000, and sometimes much higher, it is obvious that it will be 
useless to distil 500 c.c, since we should require no less than 
500 c.c. of standard ammonia to match the distillates 



CRUDE SEWAGE 51 

Before determining what quantity to use for distillation it is 
useful to filter a little of the sewage. Take 10 c.c. of the filtrate 
and dilute it with 40 c.c. of ammonia-free water in a Nessler 
glass. Then add 2 c.c. of Nessler and match this with the 
standard ammonia. If the ammonia required is less than 10 c.c, 
use 20 c.c, and if more, use 10 c.c 

Suppose we decide to use 20 c.c Pipette 20 c.c of the 
sewage into the retort or flask and add half a litre of organically 
pure ammonia-free water. 

At this stage the reaction of the sewage should be determined, 
since in some places where the refuse matter from chemical 
works accompanies the domestic sewage, it may be neutral or 
even slightly acid. If it is not found to be distinctly alkaline, a 
very small quantity of freshly fused Na 2 C0 3 should be added, 
just sufficient to render it faintly alkaline. 

The distillation is now proceeded with as in the case of 
ordinary water. 

Instead of estimating the amount of ammonia in each 50 c c, 
the first 200 c.c. may be collected in a flask and well shaken. 
20 c.c of this may then be estimated and the result multiplied 
by 10. 

Albuminoid Ammonia 

When all the saline ammonia has come over, the alkaline per- 
manganate solution is added, and the distillation proceeded with 
in the ordinary manner. 

Instead of merely adding 50 c.c of alkaline permanganate 
it is advisable to dilute this with as much as 200 c.c or 
250 c.c of distilled water and boil the mixture well for a few 
minutes. By doing this there is much less chance of the flask 
boiling dry, since it often happens that 12 or 14 Nessler glasses 
are collected before the yield of ammonia ceases. 

It is better to estimate the organic nitrogen by Kjeldahl's 
method, as is described later. 



Nitrites 

It is generally found that the reaction for nitrites is either not 
given or only very faintly. This is probably due to the fact that 
as fast as they are formed by reduction of the nitrates they are 
entirely reduced to ammonia. 



52 SEWAGE ANALYSIS 

Nitrates 

These salts are present only in minute traces. The reducing 
power of sewage is very great, so whatever nitrates are present 
are reduced rapidly to ammonia. The indigo method of estimat- 
ing the nitrates should be used, and there is seldom any need 
previously to dilute the sewage. 

Oxygen Absorbed 

20 c.c. is a very convenient quantity to take for this examina- 
tion. 1 80 c.c. of organically pure ammonia-free water are added 
and the usual 10 c.c. of standard permanganate. Even with so 
small a quantity as 20 c.c. it sometimes happens that a further 
10 c.c. of permanganate are required. 

Dissolved Oxygen 

The dissolved oxygen figure for sewage and for sewage effluents 
can be determined by the method of Winkler, which has already 
been described. 

The analysis of sewage effluents should be carried out on the 
same lines as laid down for crude sewage. The solids in suspen- 
sion should be estimated ; also the chlorides, nitrites, nitrates, 
and free ammonia. The albuminoid ammonia should be deter- 
mined by Kjeldahl's method, as the ordinary means do not give 
reliable results. 

Total Nitrogen (exclusive of nitrites and nitrates) 

KJELDAHL'S METHOD 
Apparatus, etc., required 

1. 200 c.c. flask of Jena glass. 

2. 750 c.c. distilling flask. 

3. Glass tube bent to a convenient angle with a bulb blown on 

the vertical arm. 

4. Ordinary flask. 

5. Burette. 

6. Concentrated nitrogen-free H 2 S0 4 . 

7. Nordhausen (or fuming) H. 2 S0 4 . 

8. Crystals of pure KMn0 4 . 



SEWAGE EFFLUENTS S3 

9. KOH solution 50%. 

10. 5 HC1 or H«SO. and N NaOH. 
5° 5°. 

11. Phenolphthalein or rosolic acid. 

The Process 

1. Pipette 10 cc. of the sewage into the small flask, add about 

1 cc. of H 2 S0 4 , mix well, and evaporate slowly over a small 
flame guarded by wire gauze. 

2. When the fluid is reduced to rather less than half, add 20 cc. 

of H 2 S0 4 and 3 cc. of Nordhausen H 2 S0 4 and continue to 
heat slowly. 

3. From time to time add a small crystal of KMn0 4 until the 

colour disappears very slow T ly, and continue the heating for 
about 3 hours. 

4. Allow the contents of the flask to cool, and carefully transfer 

them to the distilling flask. Wash the flask with a small 
quantity of distilled water two or three times and pour the 
washings into the distilling flask. 

5. Add 70 cc of the KOH solution and allow the mixture to 

cool. After cooling, add 30 cc more of the KOH solution, 

drop in two or three pieces of clean granulated zinc and 

carefully insert an indiarubber stopper. Connect the flask 

by means of rubber tubing with the bent glass tube so that 

the free end dips down to the bottom of a clean Erlenmeyer 

N 
flask containing 50 cc of — H 2 S0 4 , the bulb being a little 

distance above the mouth of the flask. 

6. Carefully distil until the residue is rather less than half the 

amount of the original fluid. 

7. Remove the flask containing the distillate, add a drop of 

N 
rosolic acid, and add the — NaOH carefully until the 

5° 
reaction is neutral. Read off the amount of alkali required 
and calculate the amount of NH 3 therefrom, yf of the 
ammonia calculated will represent the nitrogen. 

Explanation 

Upon boiling nitrogenous organic matter with H 2 S0 4 under 
the conditions above described, the nitrogen is slowly converted 



54 SEWAGE ANALYSIS 

into ammonium sulphate. When the process of conversion is 
completed, the H 2 S0 4 is over-neutralized with KOH, and free 
NH 3 will then distil over. 

EXAMPLE 

After the distillation was finished it was found that the 50 c.c. of 

— H SO, required 46*2 c.c. of — NaOH. 

50 So 

N 
.'. 3*8 c.c. of— H 2 S0 4 had been neutralized by the NH 3 distilled 



over 



XT 14 V8 

N 9 present = — - x ° x o'xa gramme 
2 ^ 17 1000 ^ 5 

= 1*06 milligrams. 

But this was present in 10 c.c. of the sewage effluent. 

.*. the sewage effluent contains io'6 parts per 100,000 of 
nitrogen. 

The distillation of the sewage effluent showed that there were 
10*9 parts of saline ammonia per ioo,oco. This is equivalent 
to 8*97 parts of nitrogen. 

Therefore the organic nitrogen in the sample of sewage 
effluent is io'6 - 8*97 = 1*63 parts per 100,000. 

Notes 

Great care must be exercised in heating the distilling flask at 
first, since there is a great tendency for the fluid to " bump." 
After a little time it will boil quite quietly until the ammonia 
has all been driven off, when it will once more begin to bump. 

General Considerations 

From what has been said of the varying composition of 
sewage, it may be inferred that sewage effluents also show much 
variation : and this is indeed the case. It follows from this that 
a set standard of purity is neither obtainable nor desirable. 
Each sew r age must be treated on its own merits, and the local 
circumstances taken into consideration before judgment is passed 
on an effluent. 

Whether or not an effluent causes harm to a stream depends 
mainly on two factors : firstly, on the quantity and concentration 
of the effluent • secondly, on the size and volume of the stream. 
It is obvious that an effluent, approaching crude sewage in com- 
position, would do much more harm to a small than to a large 



SEWAGE EFFLUENTS 55 

river ; and, again, a small amount of a sewage effluent would do 
less damage than a larger amount. Doubtless it would be de- 
sirable to have local standards of purification for sewage, which 
standards should take into consideration such circumstances as 
these ; and whatever standards of purity were established they 
should have for their main object the protection of rivers from 
contamination and harm. 

The injury caused to a river by the inflow of sewage or a bad 
effluent may be considerable. The water may be deprived of its 
oxygen, and the fish of the river may die : trade refuse may cause 
a like mortality. Organic matter, deposited from the sewage, 
may stink, and, ultimately, silt up the river : sewage fungus may 
grow and decay : the river may be discoloured. Finally, the 
water may be poisoned by intestinal organisms, and be made 
unfit for drinking purposes to the detriment of cattle and man. 
An effluent should not be discharged into a stream if it is likely 
to harm the water in any of these ways. 

Satisfactory Effluents 

The Royal Commission on Sewage Disposal, which was 
appointed in 1898, consider that the effect which an effluent 
has on a stream does not depend so much on the amount of 
organic matter present^ as on the condition of this organic 
matter — whether or not it is easily putrescible, and is likely to 
take up oxygen from the water. 

The Commissioners conclude that an effluent would generally 
be satisfactory if it fulfilled the following conditions : — 

1. That it should not contain more than 3 parts per 100,000 of 

suspended matter. 

2. That after being passed through filter-paper it should not 

absorb more than — 

(a) o*5 part by weight per 100,000 of dissolved or atmospheric 

oxygen in twenty-four hours \ or 

(b) vo part by weight per 100,000 of dissolved or atmospheric 

oxygen in forty-eight hours ; or 

(c) 1*5 parts by weight per 100,000 of dissolved or atmospheric 

oxygen in five days. 

An effluent which fulfils these conditions will probably not be 
putrescible. 

It may be laid down as a physical standard for all sewage 
effluents that they should not smell nor be offensive after 



56 SEWAGE ANALYSIS 

incubation for three days at 27° C. Effluents also should show 
little opacity. 

In contradiction to the Sewage Commissioners some author- 
ities consider the organic ammonia figure to be the best index of 
a satisfactory effluent. A limit of o*i parts per 100,000 has been 
advocated by some chemists ; 0*15 parts, and 0*2 parts by others. 
Some have taken the oxygen absorbed figure as a standard, and 
said that no sewage effluent ought to absorb more than 1 '4 parts 
of oxygen per 100,000 from permanganate. 

It will be seen, therefore, that really there is no chemical 
standard for a sewage effluent • and the physical standards, com- 
bined with the incubation tests, are the best means at the present 
for arriving at a decision as to the suitability of an effluent for 
discharge into a stream. 



PREPARATION OF REAGENTS 

Ammonia-free Water 

The following process is most usually adopted : — 

Distil from a large glass retort (or better, from a copper or 
tin vessel holding 15-20 litres) ordinary distilled water which has 
been rendered distinctly alkaline by the addition of sodic car- 
bonate. A glass Liebig's condenser or a clean tin worm should 
be used to condense the vapour ; it should be connected to the 
still by a short indiarubber joint. Test the distillate from time to 
time with Nessler's solution (which is described below), and when 
free from ammonia collect the remainder for use. The collection 
of water must be stopped when at least 2 litres (in such a sized 
still) remain. 

Ammonia-free Water— Organically Pure 

Distilled water, to which 1 gramme of potassium hydrate and 0.2 
gramme of potassium permanganate per litre have been added, is 
boiled gently for about 24 hours in a similar vessel to that used 
in preparing water free from ammonia, a redux condenser being 
fitted on to the top of the flask in order to return the condensed 
water. At the end of that time the condenser is adjusted in the 
usual way, and the water carefully distilled, the distillate being 



PREPARATION OF REAGENTS 57 

tested at intervals for ammonia, as in preparing the ordinary 
ammonia-free water. When ammonia is no longer found, the 
remainder of the distillate may be collected, taking care to stop 
well short of dryness. The neck of the retort or still should 
point slightly upwards, so that the joint which connects it with 
the condenser is the highest point. Any particles carried up 
mechanically will then run back to the still, and not contaminate 
the distillate. The water thus obtained should be rendered 
slightly acid with sulphuric acid, and redistilled from a clean 
vessel, again stopping short of dryness. 

Alkaline Permanganate Solution 

Dissolve 8 grammes of KMn0 4 and 200 grammes of NaOH in 
1 100 c.c. of distilled water. Boil until the bulk is reduced to 
1000 c.c. 

The object of the boiling is to drive off as ammonia any 
organic matter that may be present, either in the permanganate 
or the water. 

Metaphenylene-diamine-hydrochloride 

1 gramme of the base is dissolved in 200 c.c. of distilled water, 
and slightly acidulated with HC1. 

Nessler Solution 

1. Dissolve 35 grammes of KI in 100 c.c. of NH 3 -free H 2 0. 
2 - » 1 7 » 3) HgCl 2 „ 300 „ „ ,, 

3. „ 200 „ „ NaOH ,,1000 „ „ „ 
The HgCl 2 dissolves more quickly on heating, but it must 

be subsequently cooled. 

4. Pour the HgCl 2 solution into the KI solution until a per- 

manent precipitate of Hgl 2 is formed. 

5. Dilute this mixture to 1000 c.c. with the NaOH solution. 

The precipitate will be re-dissolved. 

6. Add more of the HgCl 2 solution until the permanent pre- 

cipitate is again formed. 

7. Allow the mixture to stand in a clean glass-stoppered bottle 

for 24 hours. 

8. Pipette off the clear fluid from time to time as required. 

When the Nessler is sensitive, it has a slight yellow colour. If 
it is colourless it will not be sensitive, and a little more HgCl 2 
solution must be added and allowed to settle in order to saturate 



58 PREPARATION OF REAGENTS 

the solution with HgCl 2 , since the sensitiveness of the Nessler 
depends upon this saturation. 

Phenol-Sulphonic Acid 

32 c.c. of concentrated H 2 S0 4 are added to 4 c.c. of pure 
phenol. These are well mixed and heated to ioo° C. for two or 
three hours, no c.c. of distilled water are then added and the 
solution is ready for use. 

Potassium Chromate Solution 

A strong solution of pure neutral K 2 Cr0 4 free from chlorine is 
required. 

Dissolve some crystals of pure K 2 Cr0 4 in pure distilled water, 
and when the solution is made, add a drop or two of the standard 
solution of AgN0 3 until a permanent red precipitate is formed. 
This ensures the absence of any chlorine in the solution. After 
the precipitate has settled, syphon or decant the clear yellow fluid 
into a small clean bottle. 

Potassium Ferrocyanide Solution 

1 gramme of K 4 Fe(CN) 6 is dissolved in 100 c.c. of distilled 
water. 

Potassium Iodide Solution 

This solution should be made as it is required, by adding 
a crystal of KI into a test-tube, and half filling it with distilled 
water. 

Before being used, a little starch solution should be added 
to a few drops diluted with water, in order to ensure the absence 
of free iodine. 

A solution of zinc iodide is frequently used instead of 
potassium iodide, since the former does not liberate free iodine 
on keeping, as does the latter. 

Starch Solution 

This solution must be made up on each occasion as it is 
required. 

As much starch as will go on to an ordinary bacteriological 
platinum loop is dropped into a clean test-tube, and the test- 
tube is three-parts filled with distilled water and well shaken. 
It is then well boiled until the liquid becomes quite clear, and 
allowed to cool, when it is ready for use. 



STANDARD SOLUTIONS 59 

Sodium Thiosulphate Solution 

Dissolve 2 grammes of the thiosulphate in ioooc.c. of distilled 
water. 

The solution undergoes changes and becomes weaker, so that 
in practice it is standardized every time it is used, by making 
control or blank experiments side by side with the sample. 

Sulphuretted Hydrogen Water 

This is made by acting on FeS with dilute HC1, passing the 
gas through a small quantity of water, and then into distilled 
water until no more H 2 S is dissolved by the water. 

The H 2 S solution must be kept in a well-stoppered bottle, and 
preferably in the dark. 

STANDARD SOLUTIONS 

General Considerations. Standard solutions are made to contain 
either a known or definite amount of a substance in a certain 
measure, or an amount sufficient to neutralize or precipitate a 
definite weight of another substance. Thus the standard 
ammonia is a solution of ammonium chloride of such a strength 
that each c.c. contains o'boi gramme of ammonia. The standard 
silver nitrate, on the other hand, contains that amount of silver 
nitrate in each c.c. w r hich exactly precipitates o'ooi gramme of 
chlorine. 

In making the standard NH 4 C1 solution we require i gramme 
of NH 3 per litre. The combining weight of the former is 

53*5 
53*5, and of the latter 17. We require, therefore, • grammes 

(i.e. 3*147 grammes) of NH 4 C1 in a litre. 

In a similar manner we require sufficient AgN0 3 dissolved 
in a litre of water to precipitate 1 gramme of CI. The c.w. of 
AgN0 3 is 1697, and that of CI 35*5. The amount of AgN0 3 

160/7 
necessary is therefore — — grammes; i.e. 4*780. Thus it re- 
mains to weigh 4*780 grammes of AgN0 3 and dissolve them in 
1 litre of water. 

The labour involved in weighing out exactly 3*147 or 4*780 
grammes is, for those who are not very adept at balance work, very 
great, and a simpler method is to weigh out a certain quantity 
exactly and to calculate the amount of water required. 



60 STANDARD SOLUTIONS 

Great accuracy can be obtained in measuring water with 
graduated flasks and pipettes. For instance, if 970 c.c. was 
the quantity required, a 1000 c.c. flask would be filled to the 
graduation mark, and 20 c.c. and 10 c.c. could be removed 
with pipettes graduated for these quantities. If 1270 c.c. were 
required, 1000 c.c. and 250 c.c. flasks could be filled and drained 
well into one holding 1500 or 2000 c.c. and 20 c.c. added by 
means of a 20 c.c. pipette. 

All standard solutions should, of course, be always kept in 
glass-stoppered bottles. 

Standard Ammonium Chloride 

NH 4 C1, m.w. 53*5 ; NH 3 , m.w. 17 

A. Strong Soaition 

Weigh out as nearly as possible 3*15 grammes of dry anhydrous 

NH.C1 and dissolve it in x 1 litre of distilled ammoma- 

free water. XTTJ 

1 c.c. =o'ooi gramme NH 3 

B. Weak Solution 

Measure 10 c.c. of " A " very accurately by means of a 10 c.c. 
pipette, and add 990 c.c. of distilled ammonia-free water. 

1 c.c. =0*00001 gramme NH 3 

Standard Calcium 

Each c.c. of the standard must contain an amount of CaCl 2 
having the same weight of Ca as 0*001 gramme of CaC0 3 . 

Weigh as nearly 1 gramme of pure crystalline calcite as possible, 

and dissolve it in the least quantity of dilute HC1 which will 

dissolve it, taking care to cover the vessel in which the solution is 

being made with a watch or clock glass to prevent the loss of 

calcium by the spitting. Evaporate to dryness over a water bath, 

dissolve again in water, and evaporate to dryness a second time ; 

in order to ensure the absence of HC1 it is advisable to repeat 

this a third time. Now dissolve the CaCl 2 in the proper quantity 

w 
of freshly boiled distilled water, i.e. — x 1000 c.c. where w is the 

weight of CaC0 3 taken. 



STANDARD SOLUTIONS 6r 

Standard Copper Solution 1 

CuS0 4 * 5H0O, m.iv. 249 • Cu, c.w. 63 

1 gramme of copper is contained in 3*95 grammes of copper 
sulphate. Weigh out as nearly as possible 3*95 grammes of the 

crystals of CuSO,, and dissolve them in x 1000 c.c. of dis- 

3*95 
tilled water. 1 cc. = o*ooi gram Cu 

Standard Indigo Solution 

Weigh out approximately 2 grammes of indigo carmine. Digest 
this with 10 grammes of Nordhausen sulphuric acid for 24 
hours. Add 30 c.c. of concentrated sulphuric acid and mix well. 
Pour this carefully into about 500 c.c. of distilled nitrate-free 
water. Wash the indigo out of the vessel with distilled water, 
a few c.c. at a time, until all the indigo has disappeared. Filter 
and make up the solution to 1 litre. 

In order to standardize the indigo solution, a burette graduated 
in y^th c.c. is filled with the solution. 2 c.c. of the standard 
nitrate solution are mixed with 18 c.c. of distilled water and 
poured into a small wide-mouthed flask. 20 c.c. of strong H 2 S0 4 
are quickly run into the flask and well mixed. The indigo is 
now run in, a few drops at a time, and the flask well shaken. 
After a certain quantity of indigo has been run in, the greenish 
colour, which quickly disappeared at first, becomes permanent. 
The amount of indigo required is next read off. Suppose the 
quantity required was found to be 2*2 c.c. 

Then 2*2 c.c. of indigo = 2 c.c. of standard nitrate; but 
1 c.c. of nitrate = 0*000014 gramme of nitrogen 

1 c.c. of indigo = — of 0*000014x2 grammes of 
nitrogen =0-0000127 gramme 

Several experiments must be made to ensure the correctness of 
these figures, and when the true figures ha"ve been found, the 
indigo should be labelled 

" 1 c.c. =0*0000127 gramme N " 

1 The standard solutions of lead, copper, and iron are made up so that 
1 c.c. =o'ooi gramme. When using it is convenient to dilute at least ten 
times. 



62 STANDARD SOLUTIONS 

Standard Iron Solution 

A. 
FeS0 4 . 7H2O, m.w. 278 ; Fe, c.w. 56 
1 gramme of iron is contained in 4*96 grammes of ferrous sul- 
phate. Weigh out as nearly as possible 4*96 grammes of the 

w 
crystals of pure FeS0 4 , and dissolve them in -7-7 x 1000 c.c. of 

distilled water. , C . C = . 00I gramme Fe 

B. 

(NH 4 ) 2 Fe 2 (S0 4 ) 4 .6H 2 0, m.w. 640 
Owing to the fact that absolutely pure FeS0 4 is difficult to 
procure, it is better to make up a standard solution with 
ammonium iron alum, which has the advantage that it is stable. 

1 gramme of iron is contained in 5 7 14 grammes of ammonium 
iron alum. 

Weigh out as nearly as possible this quantity and dissolve 

. . w 

it in x 1000 c.c. of distilled water. 

57i4 

1 c.c. = 0-0001 gramme Fe 

Standard Lead Solution 

Pb(C 2 H 3 2 ) 2 . 3H 2 0, m.w. 378*4; Pb c.w. 206-4 

1 gramme of lead is contained in 1*83 grammes of lead acetate. 

Weigh out as nearly as possible 1*83 grammes of pure lead acetate 

and add it to about 500 c.c. of distilled water, and then add 

sufficient acetic acid to render the solution clear. 

w 
Add water to make up the quantity to —~- x 1000 c.c. 

1 c.c. = 0*001 gramme Pb 
Standard Nitrate Solution 

KNO3, m.w. = ioi'i ; N, c.w, = 14 

Weigh out as nearly as possible ron grammes of KN0 3 . 

w 

Dissolve this in x 1000 c.c. of distilled water. Each c.c. 

1 on 

of the solution will contain 0001 gramme of KNO s , or be equiva- 
lent to 0*000014 gramme of N. 



STANDARD SOLUTIONS 63 

Standard Nitrite Solution 

AgN0 2 , m.w. 1 53 7 ; Ag, c.w. 1077 

Weigh out as nearly as possible 0*406 gramme of pure silver 

nitrite. Dissolve it in boiling distilled water, and add sufficient 

sodium chloride to precipitate the whole of the silver. Make the 

w 

solution up to 7 of 1000 c.c. with distilled water, and allow 

r 0.406 ' 

the silver chloride to settle. Remove 100 c.c. of the clear 

solution and dilute it to 1 litre with distilled water. 

1 c.c. = 0*0000 1 gramme N0 2 

Standard Potassium Permanganate Solution 

KMn0 4 , m.w. 316 ; 2 , m.w. 32 

K 2 Mn 2 O s + 3H 2 S0 4 - 2MnS0 4 + 3H 2 4- 5O 

i.e. 316 grammes of KMn0 4 yield 80 grammes of oxygen. The 

solution has been found most convenient when 10 c.c. of it yield 

0*001 gramme of 2 . 1 litre of the solution must contain o*i 

gramme of available oxygen. The amount of permanganate 

316 . . 

required to allow this is g— x o'i grammes in a litre \ i.e. 0*395 

gramme. Weigh out therefore as nearly as possible 0*395 gramme 

w 
of pure potassium permanganate and dissolve it in — x 1000 c.c. 

of pure distilled water (w being the weight of the permanganate 
actually taken). The solution is then to be labelled 

" 10 c.c. = o*ooi gramme 2 " 

Standard Silver Nitrate 

AgN0 3 + NaCl = AgCl 4- NaN0 3 
107*7 + 14 + 48 grammes of AgN0 3 are required to precipitate 

35*5 grammes of CI. Therefore (i.e. 4780) grammes of 

AgN0 3 will be necessary to precipitate 1 gramme of CI. 

As the solution must contain enough silver nitrate in each c.c. 
to precipitate o'ooi gramme of CI, it is evident that every litre 
should contain 4*780 grammes of the nitrate. 



64 STANDARD SOLUTIONS 

Weigh out accurately, as nearly as possible 4.780 grammes of 
pure recrystallized silver nitrate. Dissolve in about 500 c.c. of 
water in a perfectly clean chlorine-free flask ; add more distilled 

w 

water, so that the total bulk of the water shall equal ^ 

x 1000 c.c. where w is the actual weight taken. When the 
dilution is completed the solution should be poured into a 
suitable glass-stoppered bottle and kept in the dark. 

Suppose that w was found to be 5*124 grammes, then the total 

must be 5 7 of 1000 c.c. = 107 i'q c.c. 

4780 

Standard Soap Solution 

Each c.c. of the soap solution must contain an amount of soap 
which will precipitate o'ooi gramme of CaC0 3 . 

Weigh out 10 grammes of sodium oleate or the Sapo durus of 
the B.P. and mix it with a litre of equal parts of methylated 
spirit and water. 1 

Shake well from time to time and set aside in a cool place for 
24 hours. Filter into a flask which has been thoroughly well 
washed out with distilled water. 

In order to standardize the soap, it is necessary in the first 
place to find the amount of the soap which is required to make 
a permanent lather with 50 c.c. of distilled water. Suppose this 
is o*6 c.c. 

Into a 6-oz. bottle run 6 c.c. of the standard calcium solution, 
and add 44 c.c. of distilled water. Now find the quantity of the 
soap which is required to form a lather. Suppose that 5*3 c.c. 
are necessary. Then we have — 

Soap for o'oo6 gramme CaC0 3 + 5o c.c. water = 5*3 c.c. 
„ 50 c.c. water . . . . = o'6c.c. 

„ 0*006 gramme CaC0 3 . . .=470.0. 

But the soap must be of such a strength that 6 c.c. are 

required. Therefore the volume of the standardized soap must 

6 
be — of what it is unstandardized. Suppose that in this case 

the volume is 040 c.c. Then the total volume must be — of 

1 For the solution and subsequent dilution, exactly equal parts of methylated 
spirit and water should be mixed together and allowed to cool. The quantities 
of the cold mixture should be measured. 



STANDARD SOLUTIONS 



65 



940 c.c. = 1200 c.c. That means that 260 c.c. of spirit and 
water must be added so that 1 c.c. of the soap shall exactly 
precipitate 1 c.c. of the standard calcium solution. 

Standard Thiosulphate Solution 

Na 2 S 2 3 , 5H 2 0, m.w. 248 

This solution is made so that 1 c.c. = 0*00025 gramme of oxygen. 
On referring to Winkler's method for estimating the oxygen 
dissolved in water it is seen that, according to the equations, 
16 grammes of oxygen will liberate 254 grammes of iodine. 

On referring to the oxygen absorbed process it will be seen 
that thiosulphate takes up iodine, thus 

2Na 2 S 2 3 + 1 2 = 2NaI + Na 2 S 4 6 

that is, 316 grammes of thiosulphate combine with 254 of iodine. 
Thus since 16 grammes O liberate 254 grammes I, and 254 
grammes I are converted into Nal by 316 grammes of Na 2 S 2 3 , 
16 grammes O are equivalent to 316 grammes Na 2 S 2 3 . 
Na 2 S 2 3 has 5 molecules of water of crystallization ; 
.*. 316 grammes Na 2 S 2 3 = 4o,6 grammes Na 2 S 2 3 * sH 2 

. 0'00025 

1 c.c. of our standard solution must therefore contain -? — 

16 

0/496 grammes of thiosulphate, i.e. 0*00775 ; or in other words, 

7*75 grammes of crystalline sodium thiosulphate are dissolved in 

1 litre of water. 



ANALYSIS OF MILK 

Cow's milk contains proteins, carbohydrates, fats, salts and 
water. 

The average composition is : — 

Water 87*2% 



Solids 12*8%, consisting of 



Sugar, 4*8% 
Fat, 37% 
Proteins, y6% 
Ash, 0-7% 

Cow's milk, from the point of view of the hygienist, is the 
only kind of any importance. The results of a large number of 
analyses have shown that the milk of a healthy cow contains 
certain proportions of the various constituents. Although the 

5 



66 ANALYSIS OF MILK 

composition varies with the time of year, the breed of the cow, 
the interval since calving, the lactation after first or subsequent 
parturition, etc., it has been found that no milk from a healthy 
cow is worse than a certain standard. If, therefore, a sample of 
milk is examined and found to fall below this standard, in some 
manner or other, the conclusion is arrived at that cream has been 
extracted, water added, etc. 

It is therefore necessary to know what these standards are, in 
order to be able to say whether the sample of milk under exami- 
nation is normal or no. 

The determinations upon which the quality of the milk is 
decided are : — 

i. The specific gravity. 2. The total solids. 3. The fat. 
4. The total solids not fat. 5. The total ash. 6. The quality 
of the ash. 

THE SPECIFIC GRAVITY 
Apparatus required 

1. A specific gravity bottle. 

2. A good balance (sensitive to o'ooi gramme). 

The Process 

1. A specific gravity bottle holding 25 c.c. is thoroughly cleaned 

with strong HO and washed with hot water. It is then 
dried outside, and rinsed with alcohol and finally with ether. 
The ether is expelled by blowing into the bottle with the 
nozzle of a blow-pipe. 

The perforated stopper should be treated in the same 
way. 

2. About 50 c.c. of the milk and a like quantity of distilled water 

should be allowed to stand in glass-stoppered bottles in the 
laboratory for an hour or so, in order that the temperature of 
each may be that of the laboratory. 

3. The bottle is carefully weighed with the stopper and the 

weight noted. 

4. The specific gravity bottle is now filled with the water to the 

top of the neck. The stopper is then carefully inserted so 
that no bubbles of air are contained, and the water fills the 
hole in the stopper. The bottle is carefully dried outside 
with a towel, care being taken not to heat the bottle with 
the hand in the operation. 



THE TOTAL SOLIDS 67 

5. The bottle containing the water is now weighed and the 

weight noted. 

6. The bottle is next emptied, dried, and filled with the milk, 

taking all the precautions as before. 

7. It is again weighed, with the milk, and the weight noted. 



EXAMPLE 


Weight of bottle 

,, „ + water 


• 1 8 '306 grammes 

43 '3 1 4 grammes 


Weight of water . 


25*008 grammes 


Weight of bottle + milk 


44*056 grammes 


Weight of milk 


25750 grammes 


Sp. gr. of milk 


25750 
= '° n x 1000 
25*008 

= 1029*6 



Notes 

It will be observed that the temperature of both water and 
milk is that of the laboratory. This is, of course, not the 
theoretical manner of taking the specific gravity, but it is done 
in practice, and the error is very small. If it were called the 
relative density instead of the specific gravity, perhaps no objec- 
tion could be raised either to the method or title. 

A simpler method is to take the sp. gr. with a lactometer, or 
hydrometer, but this is rarely done by analysts of repute, as the 
error is greater than that obtained by weighing, owing to a variety 
of circumstances, including the temperature, the inaccuracy of 
the instrument, etc. 

Before taking the sp. gr. the milk must be well shaken, so as 
to obtain a fair sample. This statement applies to all the other 
determinations. 

THE TOTAL SOLIDS 

This determination, as in the case of water, aims at finding 
the percentage of solid constituents in the liquid, by evaporating 
the milk and weighing the residue left. 



68 ANALYSIS OF MILK 

The Process 

i . Having thoroughly cleaned and dried a platinum dish, weigh it. 

2. Weigh out in the tared dish 5 grammes of the milk after well 

shaking it. 

3. Evaporate to dryness over a water bath, inverting a glass 

funnel over the dish to prevent any dust from getting into 
the dish. The drying takes about two hours. 

4. Heat in the water oven for half an hour, and weigh the dish 

after it is cooled. 

5. Replace in the oven for a further interval and again weigh. 

If there is no decrease in the weight, this is accepted. If 
there is a decrease, the dish is placed in the oven again for 
a short time and again weighed, until two successive weigh- 
ings give no difference. 

EXAMPLE 

Platinum dish . . . = 10*324 grammes 
„ „ -t-milk . . =15*324 » 

,, „ + solids . . =10*964 „ 

Total solids . . . = 10*964-10*324 grammes 

= 0*64 gramme 
But this is the quantity in 5 grammes ; 

.". total solids % . . . . =0*64x20 

Notes = I2 ^° 

The skin that forms on the surface of the milk delays the 
drying. The formation of this skin may be prevented, and the 
process therefore hastened, by the addition to the milk, before 
evaporation, of a few drops of a mixture of one part of acetic 
acid with nine of methylated spirits. 

In order to weigh out exactly 5 grammes of milk, the dish is 
tared and 5 grammes are added to the weights already counter- 
poising the dish. Now pipette the milk in a 5 c.c. pipette and 
allow 4*7 c.c. to run into the dish on the scale of the balance, 
taking care to have the balance down. Allow the milk to run 
into the dish after this drop by drop, until upon raising 
the beam it is found that there is just too much milk. With 
a clean, small-pointed, glass rod remove a trace of the milk and 
again weigh. Wipe the rod on a clean towel and continue to 
remove traces until the milk weighs exactly 5 grammes. A little 
practice will enable the experimenter to perform the weighing 
both quickly and accurately. 



THE FAT 69 

THE ASH 

Having weighed the total solids, the dish is heated to dull red- 
ness over a Bunsen, or preferably over an Argand burner, until 
the whole of the organic matter is burnt. 

The process is expedited by breaking up the masses of dried 
milk with a somewhat stiff platinum wire from time to time. 

When the whole of the contents are of a greyish white appear- 
ance, the dish is removed to a desiccator to cool and afterwards 
weighed. 

EXAMPLE 
Weight of dish .... = 10*324 grammes 
„ +ash . . . =10*358 „ 



Ash = 0*034 gramme 

But this is the ash from 5 grammes of milk ; 

.'. the percentage of ash = 0*034 x 20 
= o*' 



THE FAT 
Apparatus required 

1. A Schmidt-Werner tube. 

2. A stout test-tube, carrying a wash-bottle arrangement. 

3. A platinum dish. 

4. A 20 c.c. pipette. 

The Process 

1. 10 grammes of milk are quickly and accurately weighed into 

the platinum dish. 

2. The Schmidt-Werner tube is clamped in a vertical position, 

after having been thoroughly cleaned and drained ; and a 
small funnel (cut short as to its tube) is placed in the mouth 
of the tube. 

3. The milk is poured down the funnel, the remains of the milk 

are then washed on to the funnel from the dish with the 
strong HC1 (which must be pure) as contained in the 
extemporized wash-bottle. The milk is then washed out of 
the funnel with the acid, and finally the sides of the tube 
are washed down with the acid, and sufficient acid added 
so that the mixture of milk and acid reaches the 20 c.c 
mark. 



70 ANALYSIS OF MILK 

4. The tube is shaken so as to mix the milk and acid well, and 

the milk is then boiled, the tube being constantly shaken. 
When the liquid is of a fairly deep brown colour, the heat- 
ing is stopped. 

5. The whole is then allowed to cool, by immersing the tube in 

water if desired. 

6. When the whole is cool, ether is poured in to the 50 c.c. 

mark. A cork is now inserted into the mouth, and the tube 
inverted gradually so that the whole of the brown liquid 
collects in the upper end of the tube. 

This must be repeated fifteen or twenty times, so that the 
ether may come into contact with, and take up all the fat. 
The tube is then held vertically and rotated quickly between 
the hands in order to get the debris to settle well, so that 
the level of the ether can be easily read. 

7. A 20 c.c. pipette having indiarubber tubing at the upper end 

is now inserted into the tube, and exactly 20 c.c. of the 
ether are sucked out of the tube. The ether can be easily 
held in the pipette by pinching the indiarubber tubing. 

8. The 20 c.c. of ether are then allowed to run into a clean 

platinum dish, which is then placed in a water oven, at 
6o° C.j in order to drive off the ether. 

9. When the ether is completely evaporated, the dish now con- 

taining the fat is weighed. 
1 o. The ether left in the tube is read off and noted for the subse- 
quent calculation. 

Explanation 

The fat in the milk being in the form of a perfect emulsion 
cannot be taken up by ether without previous treatment. Boiling 
with HC1 converts the albuminous envelopes round the fat into 
soluble acid-albumin, the fat is set free and rises to the top. The 
ether is now able to dissolve it. 



EXAMPLE 

Weight of milk taken 

„ dish 

„ dish + fat 

fat . 
Ether left in tube 

Total fat= 5LL5 x 0*326 gramme(since 
20 
0*326 gramme of fat was present in 
20 c.c. of ether) . = 0*383 gramme 



= io'ooo grammes 

= 42'3 12 
= 42*638 „ 
= 0*326 gramme 
= 3*5 cc. 



ADULTERATION OF MILK - 71 

But this quantity is present in 10 grammes of milk ; 
.'. 100 grammes contain 3*83 grammes; or the milk contains 
3-33% of fat. 

Notes 

The Werner-Schmidt tube is fixed vertically to prevent the 
milk from getting into the upper bulb, and a funnel is used to 
the same end. 

If several estimations are to be made, the 20 c.c. pipette 
should not be cleaned out, but the ether must be drained each 
time into the platinum dish. 

After having done this, it will be noticed that there is a modi- 
cum of fat lining the pipette and this amount is constant. From 
this it is evident that the first estimation done with a new or 
clean pipette will be slightly under the proper figure. 

In mixing the ether with the fat, HC1, etc., care must be taken 
not to shake the tube whilst the brown sediment and ether are 
mixed together. If it is done, a froth will be formed which is 
difficult to get rid of. 

When all the ether is at one end, that end should be well shaken, 
in order to get the ether well in contact with the walls of the tube. 

ADULTERATION OF MILK 

When a milk vendor finds that the consumption of milk 
exceeds the production, there are certain courses open to him. 
Firstly, he may refuse to supply some of his customers ; secondly, 
he may increase the production; thirdly, he may make the 
production fit the consumption. The last course is not altogether 
unknown ; and, in order to follow it, the dishonest vendor adds 
water to the milk. Sometimes he wishes to sell cream, and then 
he may deplete some of his milk of fat, and sell the resulting 
skimmed milk as genuine. 

If he abstracts cream he will raise the specific gravity of the 
milk ; if he adds water he will lower it. It may possibly occur 
to him that some of his customers have lactometers ; and so, 
judiciously, he abstracts cream and adds water. If these opera- 
tions are carefully performed, the resulting product will have a 
normal specific gravity ; and the dishonest milkman may trade 
unsuspected, until an inclement fortune sends some of his milk 
to an analyst. Such frauds in connection with milk are often 
referred to by the kindly name of sophistication. 



72 ANALYSIS OF MILK 

Standards for Milk 

In order to detect a fraudulent milk vendor, it is necessary to 
have a standard to which milk should conform ; if the milk fails 
to come up to the standard, then it can be said not to be 
genuine. 

It has been ascertained that milk, if genuine, should contain : — 
i. At least 3% of fat. 
2. At least 8*5% of solids not fat. 

And that skimmed milk, if unwatered and genuine, should con- 
tain at least 9*0% of solids not fat. 

These are legal standards ; and if a milk sample fails to attain 
to these it is considered to be adulterated and not genuine. 

Addition of Water 

When water is added to milk the specific gravity of the sample 
is lowered, and the solids both fatty and non-fatty are diminished. 
The amount of water added is determined from the amount of 
solids not fat. Thus a sample of milk was found to contain 8% 
of solids not fat; but 8*5% of solids not fat denotes 100% of 

genuine milk. Therefore 8% of solids not fat denotes — ^ 

= 94' 1 % of genuine milk ; or, in other words, about 6% of water 
has been added to the milk. 

Again, the amount of water added may be calculated from the 
ash. The ash in milk is fairly constant at 07%, although there 
is no legal standard for it. A milk sample was found to give 
o*6% of ash: now 07% of ash shows 100% of pure milk; there- 
fore o*6% of ash shows = 857% of pure milk. So 

about 15% of water has been added to this sample. 

In legal work and ordinary routine work, however, it is 
more convenient to calculate the added water from the figure 
for solids not fat, as has been shown above. 

Abstraction of Cream 

Removal of cream raises the specific gravity of milk, and lowers 
the amount of fat present. The amount of cream abstracted is 
measured by the estimation of the fat. 

Thus a sample of milk was found to have only 2*5% of fat. 



ADULTERATION OF MILK 73 

Now 3% of fat show that the fat in the milk is all present ; or a 

2't x I OO 

figure of 3 denotes 100% of fat. Therefore 2*5 denotes — 2 

= S3 , 3% of fat originally present. So more than 16% of the 
original fat has been abstracted. 

Where the fat is low and the solids not fat are average, it may 
be inferred that the diminished fat figure is due to the abstraction 
of cream and not to the addition of water. Where the fat is 
much reduced, and the solids not fat slightly reduced, it may be 
inferred that cream has been abstracted and water added. 

Rarely condensed milk is added to skimmed or watered milk 
in order to supply the deficiency in fat. The fraud is detected 
by the abnormally high figure for total solids, and by the 
increase in sugar. Condensed milk contains much sugar and 
solids — sometimes as much as 40%. 

Note 

It has been found that the specific gravity, total solids, and fat 
bear a somewhat constant relation to one another. Advantage 
has been taken of this fact, and a formula has been calculated for 
deducing the fat from the specific gravity and total solids. This 
is a great advantage when many samples of milk have to be 
estimated; because the estimation of the fat requires more 
attention than that of the total solids. 

The formula is : — 

m „ Spec. Grav. — 1000 , , 6F 

T.S. = — + 0-14 + 

4 5 

Where T.S. = Total solids, and F = fat. 

EXAMPLE 

A milk sample had a specific gravity of 1032, and had 
12*34% of total solids. Then : — 

1012 — 1000 , , 6F 

12-34 = — 5 + - I4+ — 

4 5 

.'. F = 3-5- 

Preservatives 

The most common additions to milk are sodium carbonate or 
bicarbonate, boric acid or borax, formalin, and occasionally 
salicylic acid. 



74 ANALYSIS OF MILK 



Sodium Carbonate or Bicarbonate 

is added in order to neutralize the acidity generated by the 
growth of micro-organisms, and to delay the curdling. 
These may be detected 

i. By boiling the suspected milk for an hour. After prolonged 
boiling, normal milk has only a faint tinge, but milk to 
which either of these salts has been added assumes a fairly 
deep brown colour. 

2. By the reaction on rosolic acid. To 10 c.c. of the milk 
add 10 c.c. of alcohol and a few drops of a i% alcoholic 
solution of rosolic acid. 

Normal milk will show a brownish colour, whereas milk with 
NaHC0 3 added will turn the rosolic acid a rose colour. 

Boric Acid or Borax 

The presence of these preservatives may be detected as 
follows : — 

i. Evaporate 50 c.c. of the milk, which has been rendered 
slightly alkaline, to dryness, and incinerate. 

2. Dissolve in the minimum quantity of HC1 and again evaporate 

to dryness. 

3. Dissolve the residue in a small quantity of hot water and 

moisten a piece of turmeric paper with the solution. Dry 
the turmeric paper. 

If boric acid or borax was present in the milk, the dry turmeric 
paper will assume a rose or cherry-red colour. 

The quantitative estimation is a very lengthy and delicate 
process, and beyond the scope of this work. 

Salicylic Acid 

This acid may be detected as follows : — 

1. Acidify about 25 c.c. of the milk with HC1 and filter. 

2. Shake up the filtrate well with ether and decant it. 

3. Evaporate the ether and moisten the residue with ferric 

chloride. 

The presence of salicylic acid is indicated by the development 
of a violet colour. 



ANALYSIS OF BUTTER 75 

Formalin 

The presence of small quantities of formalin in milk may be 
detected by the method suggested by Hehner. 

If a few c.c. of milk are poured into a test-tube, and a like 
quantity of strong commercial sulphuric acid is poured down the 
side of the tube so that the two do not mix freely ; at the junction 
of the H 2 S0 4 with the milk, a purple ring will be formed which 
becomes more extensive upon gradually agitating the test-tube. 

Notes 

This test is only available for formalin in milk, since no such 
reaction can be obtained with pure formalin. Pure H 2 S0 4 also 
gives no such reaction, so that the commercial acid must be 
employed. 

A still better test is as follows : — 

10 c.c. are placed in a' test-tube and 2 c.c. of 10% KOH 
solution and 1 c.c. of a watery solution of phloroglucinol are 
added. If formalin is present a pink colour will be at once 
produced. 



ANALYSIS OF BUTTER 

The term "butter" has been defined in the Margarine Act, 
1887, to "mean the substances usually known as butter, and 
made exclusively from milk or cream or both, with or without 
salt or other preservatives, and with or without the addition of 
colouring matter." 

As in the case of milk, the composition of butter varies within 
certain limits. An average pure butter has the following per- 
centage composition : — 

Fat 85-45 

Curd . . . . .2*75 

Salt ..... 3*25 

Water ..... 8*55 

but even in genuine butters the fat may vary from 82% to 87% 
and the water a corresponding amount, and no butter should be 
condemned as being adulterated with water unless it contains 
less than 80% of fat. 



76 ANALYSIS OF BUTTER 

The proximate analysis of a sample of butter may be under- 
taken as follows : — 

ESTIMATION OF WATER 
Apparatus required 

i. A platinum dish and a piece of glass rod. 

2. A water bath and a water oven. 

3. A good balance. 

The Process 

1. Weigh about 2 or 3 grammes of butter into the clean dry 

platinum dish. 

2. Place the dish on the water bath and stir from time to time 

with the glass rod, leaving the latter in the dish the whole 
time. 

3. When the visible water has evaporated, wash the fat off the 

rod with a little ether, and place the dish in the water 
oven until all the water and ether have disappeared. 

4. Remove to a desiccator until the dish is cool, and w T eigh. 

5. Replace in the oven for half an hour, again place in the 

desiccator and re-weigh. 
If the two weighings are alike or very approximate the last 
weighing may be taken as the correct weight of the dry butter. 
The loss in weight of the butter represents the water present. 

EXAMPLE 

Platinum dish . . . = 10*324 grammes 

Weight of dish + butter . . =13*524 „ 



Weight of butter . . = 3*200 „ 

Weight of dish + dried butter . =12*960 ,, 

Loss in weight . . . = 0*564 gramme 

.'. percentage of water = < L5_± x 100= 17*60 
Note 

Unless the butter is stirred from time to time during the 
process of evaporation, the melted butter floats on the surface of 
the w T ater, and so prevents its evaporation. 

Care must of course be taken to wash all the fat off the glass 
stirring rod. 



ESTIMATION OF SALT 77 

ESTIMATION OF SALT 
Apparatus required 

1. A separating funnel. 

2. The apparatus for estimating chlorine in water. 

The Process 

1. Weigh out s grammes of the butter to be analysed, and care- 

fully transfer it to a clean filter funnel, washing the remnants 
off with hot water. 

2. Pour about 200 c.c. of hot distilled water on to the butter and 

shake up well. 

3. Pour off the water into a measuring glass, pipette off 20 c.c. 

into a porcelain evaporating basin, and estimate the chlorine 
with standard silver nitrate as in the case of water. 

EXAMPLE 

Butter taken . . .5*2 grammes 

Measure of water after shaking with butter 220 c.c. 
Standard AgN0 3 required for 20 c.c. = 4*4 c.c. 

.*. 0*004 gramme CI are present in 20 c.c. of the water 
.*. butter contains 

0*004 S^'S 220 IOO o/ r -lt ^1 

f* x ^— ^ x — x % of NaCl 

1 35*4 20 5.2 /o 

= 1*42% 

Detection of Adulteration with Foreign Fats 

The most important chemical examination of butter is the 
determination of the presence of fats which are not those of 
milk. 

Margarine, which now is a good and cheap substitute for 
butter, is made chiefly of beef fat. According to the definition 
of butter given above, the addition of beef or other fat to butter 
is a legal offence, unless the mixture is sold as margarine, and it 
is illegal to mix more than 10% of butter fat with margarine. 

In order to test the properties of butter fat and margarine fat 
it is necessary to obtain these free from water, curd, salt, etc. 

Perhaps the simplest method of doing this is to fill a beaker of 
about 50 c.c. capacity with the butter and place it in the water 
oven at ioo° C. until the butter has melted, and the water, curd, 
etc., have sunk to the bottom. 



78 ANALYSIS OF BUTTER 

The supernatant fat is then carefully poured on to a dry filter- 
paper — care being taken that no water gets on to the paper — and 
allowed to filter into a clean dry beaker in the oven. 

The same method is adopted for margarine. In the process 
to be described, although butter only is used, it will be under- 
stood that exactly the same procedure is to be adopted for 
margarine. 

The general compositions of butter and margarine fats are — 



Olein 


BUTTER 
. 42*21 


MARGARIN 
30*4 


Palmitin and stearin 


■ 5° 


*oo 


69*2 


Butyrin 


4 


67) 




Caproin . 


3 


02 y 


0*4 


Caprylin . 





10) 






100 


*oo 


IOO'O 



These fats are the salts of the respective fatty acids with 
glycerol. Oleic, palmitic and stearic acids are termed non- 
volatile or insoluble fatty acids, and butyric, etc., the volatile or 
soluble acids. 

The differences in the composition of the fats are responsible 
for the chemical and physical properties which are next to be 
determined. 

Estimation of the Specific Gravity 

The procedure is similar to that adopted for determining the 
sp. gr. of milk. 

Instead of weighing at the room temperature, however, the 
melted butter fat and the clean sp. gr. bottle are placed in an 
incubator whose temperature is 37 C, for an hour. The bottle 
is quickly filled, restoppered, wiped, and replaced in the incu- 
bator for a few minutes. It is then weighed as quickly as 
possible. The sp. gr. is then calculated from the figure thus 
obtained and that obtained on weighing the same bottle full of 
water at 37° C. 

EXAMPLE 

Weight of bottle + water . . . = 18*143 grammes 
,, „ = 8*401 „ 



Weight of water . = 9*742 



DETECTION OF FOREIGN FATS 79 

Weight of bottle + butter . . . = 17*279 grammes 

• - 8> 4oi 



Weight of butter . = 8*878 

8 * 8 7 8 c 

.*. sp. gr. of butter = ot 1 

^ & 9742 

= 0-9113 

The sp. gr. of true butter fat is never below 0*911, whereas 
that of margarine never rises above 0*906. 

If we are dealing with an adulterated butter, the estimation of 
the percentage of butter present is merely a proportion sum. 

EXAMPLE 

The sample had a sp. gr. of 908*5. Find the percentage of 
adulteration. 

We must accept the lowest sp. gr. of butter, i.e. 911, and the 
highest of margarine, 906. 

x x 906 + (100 - x) 911 = 100 x 908*5 ill Li 

5^ = 250 

The Valenta l Test Modified by Jean 

This test depends upon the different amounts of glacial acetic 
acid taken up by butter and margarine respectively. 

Apparatus required 

1. A graduated test-tube 1 cm. in diameter. 

2. A graduated pipette. 

3. Water bath. 

The Process 

1. Pour 3 c.c. of the melted fat heated to 50 C. into the test- 

tube and place in the water bath at 50 C. 

2. By means of the pipette add 3 c.c. of glacial acetic acid to 

the fat. Leave the tube in the water bath until the tempera- 
ture of the whole of the contents is 50 G. 

1 The original Valenta test was as follows : Equal parts of the fat and 
acetic acid were mixed together and heated to ioo° C. They were sub- 
sequently cooled and the temperature observed at which a cloudiness appeared. 
This was found to occur with margarine at 96 '5° C. and with butter at 61 '5° C. 



80 ANALYSIS OF BUTTER 

3. Shake well two or three times and return to the bath. Allow 

the acetic acid to settle to the bottom and read off the 

height of the acid, i.e. the junction between the acid and the 

oil. 

The loss in volume of the acetic acid represents the amount 

dissolved by the fat. 

EXAMPLES 

Samples of butter and margarine were tested. The level of 
the acetic acid after the experiment was 1*2 c.c. in the butter tube, 
and 2 '2 in the margarine tube. 

1 *8 

.*. acetic acid absorbed by butter = — x 100 = 60% 

„ ,, „ margarine = — xioo = 20 , 6/ ) 

The average figures are 

Butter . . . . 63*3 

Margarine . . . .26*6 

If the sample submitted to analysis comes up to the standard 
of the above tests it can be certified as free from admixture with 
foreign fats. If, on the other hand, the sample is below the 
standards, it is well to apply a further test. This test consists in 
estimating either the volatile or the non-volatile fatty acids, or 
both. 

ESTIMATION OF THE VOLATILE FATTY ACIDS 

REICHERT-WOLLNY PROCESS 

Apparatus, etc., required 

1. Globular flask about 300 c.c. capacity. 

2. Small Thorpe's condenser. 

3. Graduated measures. 

4. Graduated burette. 

5. Two small pieces of freshly burnt pumice. 

6. Filter funnel and paper. 

7. Beakers or small flasks. 

8. — NaOH. 
10 

9. Phenolphthalein. 

10. 50% NaOH. 

11. 25% sulphuric acid. 



VOLATILE FATTY ACIDS 81 

The Process 

i. 5 grammes of the filtered butter fat are poured into the flask 
and 2 c.c. of the 50% NaOHand 10 c.c. of absolute alcohol 
are added to the butter. 

2. A reflux condenser is fitted to the flask, and the latter is 

placed over a water bath at ioo° C. The flask is shaken 
from time to time and the boiling continued for about half 
an hour. 

3. The condenser is disconnected from the flask and the alcohol 

is allowed to evaporate. 

4. 100 c.c. of distilled water are poured in the flask, the whole 

shaken up well, and placed on the water bath for a quarter 
of an hour. 

5. 4 c.c. of 25% H 2 S0 4 are mixed with 36 c.c. of distilled water 

and poured into the flask. At the same time the two small 
pieces of pumice are dropped in the flask. 

6. A cork is inserted into the neck of the flask, carrying a tube 

bent at an obtuse angle and having a bulb blown on it 
close to the cork. The whole is then connected to a con- 
denser and within 28-32 minutes exactly no c.c. are 
distilled into a measure through a funnel carrying a filter- 
paper. 

7. 100 c.c. of the distillate are taken, and to this 1 c.c. of phenol- 

phthalein is added. 

8. The decinormal caustic soda is then run into the distillate 

until a permanent rose-pink is obtained. The number of 
c.c. of soda is noted. To the number used one-tenth is 
added. 

9. This number of c.c. of decinormal soda is known as the 

" Reichert-Wollny Number " of the butter or fat. Butter 
gives a Reichert-Wollny number of not less than 24. 
Margarine gives a Reichert-Wollny number of not less than 
3. Mixtures of margarine and butter give Reichert-Wollny 
numbers between 3 and 24. 

Explanation 

Boiling the fat with alcoholic soda converts the glycerol salts 
into soda salts and glycerin. 

C 3 H 5 (C 4 H 7 2 )s + 3 NaOH = C,H B (HO) 8 + 3 NaC 4 H 7 2 

(glycerin) (sod. butyrate) 

6 



82 ANALYSIS OF BUTTER 

The reaction for the butyrate is similar to that for all the others, 
oleate, stearate, etc. 

The addition of the sulphuric acid decomposes the sodium 
butyrate, etc. ; butyric acid, etc., are set free and are distilled 
over by heat 

2 NaC 4 H r 2 + H 2 S0 4 = Na 2 S0 4 + 2C 4 H 8 2 

The object of filtering the distillate is to free it from traces of 
the non-volatile acids which almost invariably distil over. 

Pumice is added to prevent the " bumping " which so often 
accompanies the distillation of any liquid containing sulphuric 
acid. 

EXAMPLE 

Five grammes of butter fat gave a distillate, ioo c.c. of which 

N 
required 26*8 c.c. of — NaOH to neutralize it. 

Observe that no c.c. were distilled and only 100 c.c. neutral- 
ized. The acidity of the whole distillate will therefore obviously 

be — x 26*8, or one-tenth more than the observed quantity, 

namely, 29*48. This is the Reich ert-Wollny number of this 
butter fat, and shows genuine butter. 

Suppose the figure obtained had been 18. What percentage 
of adulteration with margarine would this show ? 

Let x = the percentage of adulteration (i.e. of margarine). 
Then x+ 3 + (100 -^24 =100x18 

2IX = 60O 

* = 28-5% 

Notes 

The Reichert-Wollny number does not give an exact estima- 
tion of the volatile fatty acids present in the butter fat. It is 
an empirical figure only, and in order that it may be obtained 
accurately, strict care must be taken in, performing the various 
operations ; the apparatus must be of standard Reichert-Wollny 
size ; and the distillation must be completed within the specified 
time. Under such standard conditions butter fats invariably yield 
figures over 24 ; other fats (with the exception of cocoanut oil) 
give numbers of less than 3. Cocoanut oil may give a Reichert- 
Wollny number at 7-8. 



INSOLUBLE FATTY ACIDS 83 

ESTIMATION OF THE INSOLUBLE FATTY ACIDS 

Instead of estimating the volatile, the insoluble fatty acids may 
be estimated. In order to do this, the fat is saponified as before. 
After saponification it is transferred to a litre flask, and the small 
flask is washed two or three times with hot water, the washings 
being added to the contents of the large flask. 4 c.c. of 25% 
H 2 S0 4 are mixed with 30 or 40 c.c. of hot water and poured 
into the flask, which is then carefully filled to within an inch of 
the top of the neck with hot water. The fatty acids will now 
collect on the top of the water. 

The mouth of the flask is covered over, and the contents are 
allowed to cool. When the flask is cold, the mass of fatty acids 
can with a little care be loosened by means of a glass rod from 
the sides of the neck, and transferred en masse to a clean porce- 
lain evaporating basin. The water remaining in the flask is now 
filtered through a filter-paper, and when the filtration is complete 
both paper and flask are allowed to dry. 

The mass of fatty acids is dissolved in ether and filtered 
through the dried filter-paper in a tared platinum dish, and the 
basin is washed free of fatty acids with a little ether. The large 
flask is now washed out with ether, and the ether filtered. 
Finally the filter-paper is washed with ether, so that all the fatty 
acids are in the platinum dish. The ether is next evaporated in 
the water oven, and the dish is weighed. The gain in weight 
represents the amount of the insoluble fatty acids. 

Note 

In butter fat the insoluble fatty acids form about %%%. In 
margarine and other fats they are about 96%- 

Preservatives 

The common preservative added to butter is boric acid or 
borax. The detection of this is performed in exactly the same 
manner as in the case of milk. 



8 4 



ANALYSIS OF FLOUR 
ANALYSIS OF FLOUR 



A good wheaten flour has the following average percentage 



composition : — 








Starch 


• 597 


Soluble nitrogen . 


i-8 


Dextrin 


7-2 


Fat . 


1*2 


Cellulose . 


i*7 


Mineral matter . 


r6 


Gluten 


12*8 


Water 


I/l'O 




Total . 




IOO'O 



The chemical analysis of a sample of flour for adulteration is 
usually confined to the determination of the percentage of water, 
gluten, ash, and mineral matter. 

The best practical and domestic test to apply to flour is to use 
it for making bread. A good flour makes good bread. 

ESTIMATION OF THE PERCENTAGE OF WATER 

5 grammes af flour are weighed in a platinum dish, and dried in 
the water oven until a constant weighing is obtained. The loss 
in weight represents the water present, and the percentage is 
calculated therefrom. In a good sample of flour the percentage 
of water should not exceed 18. 

ESTIMATION OF THE ASH 

After the dried flour has been weighed it is incinerated in the 
platinum dish, and the residue weighed. 

The percentage of ash varies from 0*5% to 1%, but should not 
exceed this latter figure unless mineral matter has been added. 

ESTIMATION OF THE GLUTEN 

1 . Weigh 50 grammes of flour, mix it carefully and thoroughly with 

50 c.c. of distilled water, and allow it to stand for an hour. 

2. Collect the paste thus made in a linen handkerchief, and make 

the latter into a bag. 

3. Allow water from a tap to run on the outside of the bag and 

knead the paste well until the water running away is clear. 

4. Remove the paste from the bag and complete the kneading in 

the hand until the water which runs away is quite clear. 

5 . Squeeze the mass and remove all the extraneous water and weigh. 
The moist gluten should form from 25% to 30% of the 

weight of the flour. 

6. Dry the gluten in a platinum evaporating basin and weigh again. 
The dry gluten should be 12% to 15% of the flour. 



BREAD 



85 



Note 

Old or musty flour will not produce an adhesive mass which 
can be kneaded, but a semi-liquid mass which easily washes 
away. No such mass of gluten can be obtained with rye flour, 
however good and new it may be. 

ESTIMATION OF MINERAL MATTER 
The Chloroform Test 

If flour which contains added mineral matter be shaken up 
with chloroform the flour will float in the chloroform, whilst the 
mineral matter very quickly sinks to the bottom. 

If the majority of the chloroform be poured off, and the 
sediment shaken up with fresh chloroform two or three times, 
the mineral matter can be obtained free from flour. 

The sediment being washed out of the test-tube and the chloro- 
form evaporated, is now ready- for qualitative examination. 

If alum has been added to the flour (a rare proceeding, since 
it is not usual to add it until the flour is in the process of bread- 
making) it will be detected in the sediment, as it is only very 
sparingly soluble in chloroform. 

ERGOT 

Flour, and particularly rye flour, is liable to be ergotized, and it 
is necessary for the student to know how to detect the presence 
of this drug. This may be done by warming some of the 
suspected flour with a solution of KOH. If ergot is present 
the characteristic odour of propylamine will be detected. 

Ergot may also be detected by shaking up 2 grammes of the 
suspected flour in 10 c.c. of 70% alcohol containing w HC1. 
If ergot is present, after a short time a blood-red colour will 
develop. 





ANALYSIS OF 


BREAD 




An 


average sample of 


bread has 


the 


following percentage 


composition : — 












Starch, dextrin, 


maltose . 






5*'3 




Proteins . 










6-5 




Fat 










I'O 




Ash 


. 








i"o 




Water . 


• 








40*0 



IOO'O 



86 ANALYSIS OF BREAD 

The chemical analysis of a sample of bread is usually confined 
to the determination of the acidity, the ash, and the presence of 
alum. 

THE ESTIMATION OF THE ACIDITY 

Acetic and lactic acids are both present in bread, but the 
acidity is usually calculated in terms of acetic acid. 

In order to ascertain the acidity, grate a certain quantity of the 

bread crumb and weigh 20 grammes of the crumbs. Transfer these 

into a beaker and add 100 c.c. of hot distilled water. Stir well 

and allow it to stand for two or three hours. Filter 25 c.c. into 

a flask or evaporating basin and add a drop of phenolphthalein. 

N 
Add — NaOH from a burette until the fluid is neutral. From 
10 

the amount of alkali used calculate the amount of acid. 

EXAMPLE 

20 grammes of bread-crumb w T ere taken. 

N 
2 z c.c. of the extract took q*6 c.c. of — NaOH. 

J ^ 10 

The 20 grammes of bread yielded therefore an acidity equal to 

N 
^8*4 c.c. of — NaOH. There was therefore as much acid as in 
* 10 

N 
38*4 c.c. of — acetic acid. The molecular weight of acetic acid 

N 
is 60. Therefore 100 c.c. of — acetic acid contain o*6 gramme 

10 ° 

of acetic acid. 

. 3S*4 

.*. ^8*4 c.c. contain- — x o*6 gramme 
o t IOO & 

= 0*2304 gramme 

100 grammes of the crumb would contain 5 x 0*2304, i.e. 1*15 
grammes of acetic acid. 

ESTIMATION OF THE ASH 

The estimation of the ash is performed in a manner similar to 
that which has been previously described. 

If the ash exceeds 2% there will be a suspicion of added 
mineral matter. 



ESTIMATION OF ALUM 87 

DETECTION OF ALUM 
In order to detect the presence of alum in bread, a slice should 
be cut from the middle of the loaf and a few drops of a mixture 
of a fresh solution of logwood in alcohol and a saturated solution 
of ammonium carbonate should be poured on to the centre of the 
slice. When the fluid dries up a distinctly blue colour will develop 
if alum is present. If no alum is present the colour will be brown. 

ESTIMATION OF ALUM 

The estimation of alum is a somewhat lengthy process, but 
may be performed in the following manner : — 

100 grammes of bread are carefully incinerated in a platinum 
dish until the ash does not decrease in weight. After cooling, 
3 c.c. of pure strong HC1 are added, and the whole diluted with 
20 or 30 c.c. of water. The fluid is then boiled and filtered. 

The residue should be dried, incinerated, weighed and returned 
as silica. 

The filtrate is now alkalized with ammonia, when the phos- 
phates of calcium, magnesium, iron, and aluminium will be 
thrown down. The fluid is now made strongly acid with acetic 
acid, boiled, and filtered. The residue consisting of the phos- 
phates of iron and aluminium is now dried and weighed. After 
the weight has been ascertained, the residue is dissolved, the iron 
estimated colorimetrically and deducted from the total residue. 
The remainder will represent the phosphate of aluminium, and 
from this the amount of alum can be calculated. 

In order to be able to say whether alum has been added to 
bread it is first necessary to deduct the alumina which is present 
normally in bread. It has been found that in a normal sample 
of bread there is as much alum as silica. The weight of silica 
found must therefore be deducted from the amount of alum 
found, and any excess will represent added alum. 

ANALYSIS OF COFFEE 

Coffee is frequently sold mixed with chicory, a preparation from 
the root of the wild endive. When it is sold as a mixture no legal 
objection can be taken to it. Sometimes it happens, however, 
that such a mixture is sold as pure coffee : this constitutes a 
fraud, and it becomes necessary to know whether any sample of 
coffee has been adulterated. The usual adulterant is chicory, 
and the detection of this substance only will be treated here. 



88 ANALYSIS OF COFFEE 

Qualitative Tests for Chicory 

A. Put some of the suspected coffee upon the surface of some 

water in a tall beaker or cylinder. Roasted chicory sinks 
at once, making a brown trail in the water through which it 
passes ; coffee will float for several minutes, and takes 
longer than chicory to colour the water. 

B. The smell of chicory is different from that of coffee. 

C. Examine with the microscope. Chicory shows typical " dotted 

ducts." 

D. Heat some of the sample in a platinum dish until it is reduced 

to ash. The ash of coffee is almost white ; chicory contains 
more iron, and the ash has a reddish colour. 

E. Take 5 grammes of the suspected coffee, and pour into it 30 c.c. 

of boiling water. Filter into a Nessler glass and add 5 c.c. 
of lead acetate solution. This will precipitate the colouring 
matter of coffee, leaving the supernatant fluid colourless ; if 
chicory is present the column of fluid will retain its brown 
colour. 

ESTIMATION OF AMOUNT OF CHICORY 

FIRST METHOD 

Specific Gravity of a 10% Extract 

1. Weigh exactly 10 grammes of the sample of coffee, and place 

the coffee in a beaker. 

2. Make a paste of the coffee with a little distilled water, and 

then dilute so that exactly 100 c.c. of w r ater are present. 

3. Cover the beaker and leave it for 10 or 12 hours. 

4. Filter 50 c.c, fill into a specific gravity bottle and weigh. 

5. Calculate the specific gravity, and from this the percentage of 

adulteration. 

EXAMPLE 

The average specific gravities of 10% extracts of coffee and 
chicory are respectively 1*009 an d 1*024. The specific gravity of 
the 10% extract of a sample of mixed coffee and chicory was 
found to be 1*0139. 

If x is the percentage of coffee in the mixture it is obvious that 
x x 1009 + (100 -a;)io24 =100x1013*9 
i$x = 10 10 
x = 67'3 
That is, there is 32*7% of chicory. 



ESTIMATION OF CHICORY 



89 



Table giving the Approximate Percentages of Coffee in 
a Mixture of Coffee and Chicory from the Specific 
Gravity of a 10% Extract. 



Percentage of 


Sp. gr. of 10% 


Percentage of 


Sp. gr. of 10% 


Coffee 


Extract 


Coffee 


Extract 


IOO 


1009 00 


45 


I0I7*25 


95 


IOO975 


40 


IOI800 


90 


1010*50 


35 


IOlS'75 


*5 


1011*25 


30 


1019*50 


80 


IOI2 00 


25 


1020*25 


75 


1012*75 


20 


1021*00 


70 


1013*50 


15 


1021*75 


65 


1014*25 


10 


1022 50 


60 


1015*00 


5 


I023*25 


55 


IOI57S 





1024*00 


50 


IOl6*50 


~ 


~ 



SECOND METHOD 
The Determination of the Soluble Ash 

A weighed quantity of coffee is placed in a platinum dish and 
incinerated. After cooling, the ash is treated with distilled water 
until all the soluble matter has been dissolved. The solution is 
then filtered, the dish and paper washed with distilled water, the 
filtrate transferred to a tared platinum dish and evaporated to 
dryness. The dish is then weighed — the increase in weight 
representing the amount of soluble ash. From the weight the 
percentage is calculated. In order to determine the adulteration, 
it is assumed that chicory never yields a soluble ash greater in 
amount than 17%, and that coffee yields a soluble ash never less 
than 3%. 



ANALYSIS OF SPIRITS 

These, with the various liqueurs, contain a large proportion of 
alcohol. The Sale of Food and Drugs Amendment Act, 1879, 
fixes the minimum of alcohol for spirits. 

Whisky, brandy, and rum must not be more than 25 under 
proof. 

The term "proof spirit" arose when the test applied was to 
moisten gunpowder with the spirit in question. On applying a 



90 ANALYSIS OF SPIRITS 

light, if the gunpowder burnt, the spirit was said to be proof or 
over proof; if it did not, it was under proof. It has been subse- 
quently denned by Act of Parliament to be a mixture of alcohol 
and water of such a density that the weight of 13 volumes at 
51 F. shall be equal to that of 12 volumes of water. According 
to this definition, proof spirit contains 49*24% by weight and 
57*06% by volume of alcohol. 

25 under proof corresponds, therefore, to about 43% by volume 
of absolute alcohol. 

Gin may be as much as 35 under proof, i.e. need only contain 
about 37% by volume of alcohol. 

Alcohol 

To determine the amount of alcohol present in a sample of 
s P lrlt ' Apparatus required 

1. Small distilling apparatus with Argand burner. 

2. Specific gravity bottle. 

The Process 

1. 100 c.c. of the spirit are measured into the distilling flask. 

2. The spirit is distilled over the Argand burner until it is all but 

dry. 

3. The distillate is made up to 100 c.c. by the addition of dis- 

tilled water and well mixed. 

4. The specific gravity of a portion of this is now taken by the 

aid of the specific gravity bottle. 

5. From the tables 1 the percentage of alcohol is read. 

Acidity 

Nearly all spirits have a slight acidity, due either to volatile 
acids (which are returned in terms of acetic acid) or to fixed 
acids (which are returned as tartaric acid). 

The following are approximate figures : — 

TOTAL ACIDITY % 

Brandy . ... o*oi to 0*05 

Rum . . . . 0*5 

Whisky . . 01 

To determine the acidity. 
1. 50 c.c. of the spirit are measured into a flask, and a few drops 
of phenolphthalein are added. 

1 These tables are of such a length that they have been relegated to the 
Appendix. 



ANALYSIS OF SPIRITS 91 

2. Decinormal soda is added drop by drop until the point of 

neutrality is arrived at. 

3. The percentage acidity is then calculated. 

Brandy being made from grapes, the acidity is returned in 

N 
terms of tartaric acid (1 c.c. — NaOH = 0^007 5 gramme tartaric 

acid). IO 

For other spirits the acidity is in terms of acetic acid (1 c.c. 

N 
— NaOH = 0*006 gramme acetic acid). 

Sulphuric acid is sometimes present, but the estimation of the 
free acid is beyond the scope of this work. 

The residue of the various spirits and the ash resulting from 
them vary. c/ 0/ 

J RESIDUE% ASH % 

Brandy . . 1 to 1*5 0*04 to 0*2 

Whisky . . . 07 mere trace 

Rum . . .' 07 to 1*5 o*i 

Gin (sweetened) . 5 to 6 

The residue is obtained by evaporating a measured quantity 
in a tared platinum dish, and weighing. The difference in weights 
is the amount of residue. This is then burnt, and the ash 
weighed. The percentages are then calculated. 

Tannin 

Any amount of tannin more than mere traces may be detected 
by adding a few drops of perchloride of iron solution to the 
spirit. A darkening in colour is indicative of this substance. 



ANALYSIS OF WINES 

The determination of the alcohol and the residue is made as 
in the analysis of spirits. There is an additional determination 
necessary, namely, the estimation of the volatile acidity. 

a. Total acidity. ^ 

25 c.c. of the wine are measured into a beaker and titrated 

TT NaOH, the colouring matter in most wines acting as an 
effective indicator. The acidity is returned in terms of tartaric acid. 



92 



ANALYSIS OF WINES 



b. Volatile acidity. 

This may be determined in two ways : — 

(i) 25 c.c. of the wine are diluted with 200 c.c. of distilled water 

and distilled until only about 20 c.c. are left in the retort. 

N 
The distillate is then titrated with — NaOH and the acidity 

10 

returned in terms of acetic acid. 

(2) 25 c.c. of the wine are evaporated over a water bath almost 

to dryness, the residue is dissolved in distilled water and 

titrated as before. The difference between the total acidity 

and that now found will represent the volatile acidity. 

Table (after Dupre) showing the Proportions of the 
above Constituents in a few Wines (grammes per cent). 



Alcohol 


Fixed 


Volatile 


Total 


Dry 


acidity 


acidity 


acidity 


residue 


Hock . . 


9*56 


•348 


•057 


•420 


i-86 


Claret 


8*53 


•424 


•147 


•608 


2*14 


Sherry 


17*20 


270 


•153 


•461 


4*20 


Madeira 


1775 


•326 


•168 


•536 


4'34 


Port . 


18-56 


•308 


•084 


•413 


7'55 


Champagne 


9*22 


— 


— 


•580 


II*20 



Some wines contain free sugar, whilst others, such as some of 
the Spanish wines, are " fortified " by the addition of alcohol. 



ANALYSIS OF BEER 

The determinations required in the case of beer are alcohol, 
fixed, volatile and total acidity, and solid residue, and the opera- 
tions are performed exactly as in the case of wine. 

The fixed acidity is returned in terms of lactic acid, so that 1 c.c. 

N 

— NaOH = o'ooo gramme lactic acid. 
10 y & 

The best test for the bitter used, whether hop or other, is by 
means of the taste. 

It is well known that in England the beer is brewed with what 
is termed a top yeast, whilst the well-known Lager beers are 
brewed with a bottom yeast. In consequence, there is a distinct 
difference in the amount of alcohol formed. In English beers 
the alcohol forms 4% to 6%, in German beers from 2% to 5%. 



ANALYSIS OF BEER 93 

The acidity is fairly constant, about 0*16%, and the residues vary 
from 2*5 to 15%. 

Arsenic in Beer 
During the winter of 1 900-1 901 there was a large outbreak of 
arsenical poisoning among beer-drinkers, chiefly in the northern 
parts of England. The beer that gave rise to this poisoning had 
been manufactured, not from malt, but from invert sugar, which 
was prepared by the action of dilute sulphuric acid on rice and 
other starches. Dilute commercial sulphuric acid may contain 
arsenic, derived from the iron pyrites used in its manufacture, 
and some invert sugars, made by this process, yield as much as 
two grains of arsenious acid to the pound. Some of the beers 
analysed during the outbreak of poisoning showed as much as 
a grain per gallon of arsenious acid, which is one hundred times 
the maximum allowed by the Royal Commission on Arsenical 
Poisoning. 

Test for Arsenic 

The most convenient test for this metal is that of Reinsch. 
Some of the beer is placed in a beaker, and acidulated by dilute 
pure hydrochloric acid. A small piece of bright arsenic-free 
copper foil is suspended in the liquid, and the whole is then 
boiled for half an hour and allowed to cool. If the copper foil 
is unaffected, no arsenic is present : if, on the other hand, there 
is a grey or black deposit, then arsenic (or antimony) is probably 
contained in the beer. The copper foil is then washed with 
water, dried, and placed in a test-tube over the mouth of which is 
a cover-glass. The tube is heated gently over a Bunsen burner, 
when the arsenic is oxidized and sublimes and condenses on the 
cool part of the tube and on the cover-glass. Upon examining 
the deposit under the microscope the tetrahedral or octahedral 
crystals of arsenious oxide are seen. If the deposit on the copper 
is antimony, the microscopic examination shows only an amor- 
phous deposit. 

With suitable and obvious modifications this test of Reinsch for 
arsenic may be applied to the detection of the metal in food, 
artificial flowers, wall-papers and other substances in which the 
presence of arsenic is suspected. 

VINEGAR 

Vinegar is the well-known condiment, the essential ingredient 
of which is acetic acid. 



94 ANALYSIS OF VINEGAR 

Two points are important concerning vinegar. First, that it 
shall contain at least 3% of acetic acid, and secondly, that it shall 
not contain more than the merest traces of free mineral acid. 

Estimation of the Acetic Acid 

The vinegar may be titrated directly with — NaOH, using 

phenolphthalein as indicator. 10 c.c. of the vinegar are diluted 

with an equal quantity of distilled water before, titrating. The 

N 
acetic acid is calculated directly from the soda : 1 c.c. — NaOH 

10 

= 0*006 gramme acetic acid. 

Detection of Free Mineral Acid 

Sulphuric acid is the acid most commonly found, although 
hydrochloric acid has been found. The detection of free acid 
is easily determined by placing a few drops of vinegar and a drop 
of a watery solution of methyl violet upon a white slab, the two 
fluids being separate. With a glass rod, a portion of the methyl 
violet is brought into contact with the vinegar. If no free 
mineral acid is present the colour remains. If only a trace of 
free acid is present the violet changes to blue, and if more than 
*i% is present a distinctly green colour develops. 

A further test consists in testing the reaction of the ash. If a 
pure sample of vinegar be incinerated the ash will be alkaline, 
owing to the fact that the organic salts are converted into car- 
bonates upon heating. If free mineral acid is present the ash 
will be less alkaline, or even neutral if more than traces are 
present. 

LEMON JUICE AND LIME JUICE 

These juices are always kept on board ship, and the Board of 
Trade standards are that the juice shall have a specific gravity of 
at least 1*030, and shall have an acidity equal to 30 grains per 
ounce of citric acid (6*8%). 

The specific gravity is determined in the manner previously 
described. 

The acidity, which is due to the presence of citric and malic 

N N 

acids, is determined by titrating; with — NaOH (1 c.c. — NaOH 
J ° 10 v 10 

= 0.006 gramme citric acid), and returned in terms of citric acid. 

Free mineral acids are determined as in the case of vinegar. 



ANALYSIS OF AIR 

ESTIMATION OF OXYGEN IN AIR 
Apparatus, etc. 

i. Hempel's gas-absorption bulbs. 

2. Two graduated cylinders, one furnished with a fine nozzle and 

glass tap, and bent at right angles at the other end, and the 
second one bent at right angles at one end and funnel-shaped 
and open at the other, the two bent ends fitting in wooden 
supports and connected together with indiarubber tubing, 
2 ft. The rubber tubing should not connect the two tubes 
directly, but should have a piece of glass tubing inserted 
about the centre. 

3. An alkaline solution of pyrogallic acid. 

The Process 

1. Fill the Hempel bulbs with the pyrogallic acid so that the 

lower bulb is full and the level of the pyrogallic acid in the 
U-shaped capillary tube at a certain point, w T hich is recorded 
by making a pencil mark on the white enamel behind. 
Attach short lengths of rubber tubing to the open ends, and 
clamp. 

2. Place the two cylinders A (the one provided with a stop-cock 

and nozzle) and B (the levelling tube) on the table and pour 
water into B until each tube is about half full. Now raise 
B. The air in A will be expelled as the level of the water 
rises. When all the air is expelled close the tap. 

3. The apparatus being in the place whose air is to be examined, 

the tube B is lowered and the stop-cock of A opened. The 
air will enter into A. When about 50 c.c. have entered, the 
stop-cock is closed. B is now raised or lowered as required 
to bring the water in the tubes to the same level, and the 
quantity of air noted. 

4. The capillary tube of the absorption bulb is connected with 

the nozzle of A by the short indiarubber tube and the clamp 
undone. 

95 



96 



ANALYSIS OF AIR 



5. The stop-cock of A is now opened and the tube B is raised. 
The air is by this means driven over into the absorption 
bulb. The stop-cock is now closed. The bulb may be 
carefully disconnected after clamping the tube, and shaken 
gently. 




FIG. I. HEMPELS BULB 



ESTIMATION OF CARBON DIOXIDE 97 

6. After about 15 minutes the tube A is again connected, the 

stop-cock opened, and the tube B lowered until the level of 
the pyrogallic acid in the capillary tube is the same as 
before the operation. 

7. The tube B is again adjusted so that the level of the water in 

A and B is the same, and the quantity of air in A is noted. 

The difference between the first and second readings will give 
the amount of oxygen absorbed, and this difference multiplied by 
100 and divided by the original bulk will give the percentage of 
oxygen in the air. 

Expired air may be examined in the same manner. In order 
to collect the expired air, the tube A should be filled with water 
by raising A as before, and the air may be simply blown down 
the nozzle from the mouth. 

This method is not sufficiently delicate for the estimation of 
C0 2 in ordinary air, and other methods have to be adopted. 
These are described below. 

ESTIMATION OF CARBON DIOXIDE 

1. PETTENKOFER'S METHOD 

Apparatus, etc. 

1. A large bottle. 

2. A 50 c.c. and a 25 c.c. pipette. 

3. A 50 c.c. burette. 

4. A small Erlenmeyer flask. 

5. Standard oxalic acid, 1 c.c. =0*5 c.c. C0 2 . 

6. Baryta water. 

7. Solution of methyl orange or phenolphthalein. 

The Process 

1. The large jar must be accurately gauged by filling with water 

to the top and inserting the stopper, and then measuring the 
amount of water. 

2. To fill the jar with the air, first fill it with water and empty 

the water in the room, the air of which is to be sampled. 

3. Add 50 c.c. of baryta water by means of the pipette and 

replace the stopper. Shake up well and allow 7 the jar to 
stand for about an hour, shaking from time to time. 

4. Meanwhile, measure 25 c.c. of the baryta water into an Erlen- 

meyer flask, add a drop of methyl orange and titrate with 
the standard oxalic acid. Note the number of c.c. used. 



98 ANALYSIS OF AIR 

5. When the baryta water has been in contact with the air for a 

sufficiently long time, remove 25 c.c. of the baryta water 
with the pipette and allow it to run into another Erlenmeyer 
flask. 

6. Add a drop of methyl orange and titrate with the oxalic acid, 

noting the number of c.c. used. 

Explanation 

The baryta water when in contact with the C0 2 absorbs it, and 
barium carbonate is formed, which is insoluble. 
Ba(OH) 2 + C0 2 = BaC0 3 + H 2 

As BaC0 3 is an insoluble neutral salt, the alkalizing power of 
the Ba(HO) 2 is diminished in proportion to the amount of the 
salt formed. 

In titrating with the oxalic acid the BaC0 3 is unaffected by the 
weak acid, and the whole of the acid used is expended in con- 
verting the Ba(OH) 2 into Ba(COO),. 

Ba(OH) 2 + (COOH) 2 = Ba(COO) 2 + 2H 2 
Therefore the difference between the quantity of oxalic acid used 
to neutralize the 25 c.c. of Ba(OH) 2 which has not been in 
contact with the air, and that required to neutralize the Ba(OH) 2 
which has been in contact with the air, will represent the amount 
of Ba(OH) 2 converted into BaC0 3 . 

But the oxalic acid was prepared so that 1 c.c. should be the 
equivalent of 0*5 c.c. of C0 2 ; therefore each c.c. of difference 
= 0-5 c.c. of C0 2 which has converted the Ba(OH) 2 into BaC0 3 . 

EXAMPLE 

The jar was found to contain 3950 c.c. 

50 c.c. of baryta water were run into the jar, therefore the air 
experimented upon was 3950-50 = 3900 c.c. 

On titrating the Ba(OH) 2 it was found that 25 c.c. of the fresh 
solution required 22-50 c.c. of standard acid to neutralize. 
The Ba(OH) 2 from the jar took 19*35 c.c. 

25 c.c. of original Ba(OH) 2 . . =22*50 c.c. acid 
25 c.c. of used Ba(OH) 2 . . . =19-35 » 

Difference of acid used . . = 3*15 „ ,, 

But 1 c.c. acid = 0*5 c.c. C0 2 at o° C. and 760 mm. of mercury, 
.*. C0 2 taken up by 25 c.c. of Ba(OH) 2 = 3.i5 c.c. 



ESTIMATION OF CARBON DIOXIDE 99 

As 50 c.c. were used, the C0 2 absorbed by the Ba(OH) 2 = 
3.15 c.c. 

Now this 3*15 c.c. were present in 3900 c.c. 

.'. there were 315 x Jfgg c.c. of C0 2 % - o*8o% 

Notes 

In manipulating the jar for emptying, filling, etc., care must be 
taken not to handle it with the naked hands, as by so doing the 
sides of the jar will get heated, and the volume will not be 
correctly obtained, since the air will expand. 

The baryta water must be run into the jar and removed with 
all expedition, and care must be taken not to breathe into the jar 
during any of the manipulations. The same care must be taken 
with the flasks during titration, etc. 

It is not necessary to wait for the baryta water to clear before 
pipetting it out for titration, since, as has been said, dilute oxalic 
acid does not decompose the barium carbonate. 

In calculating the C0 2 present per thousand in the jar, in the 
above example, no notice has been taken of the fact that 1 c.c. 
of the acid corresponds to 1 c.c. of C0 2 at o° C. and 760 mm. of 
mercury, and not to 1 c.c. at the room temperature and pressure. 

To correct for this it is only necessary to multiply the 3*15 by 

760 T 

-5-, and this by , when P is the height of the barometer, and 

Jr J 273 ° 

Z'the absolute temperature of the room. 

Standard Oxalic Acid 

(1 c.c. =0.5 c.c. C0 2 at N.T.P.) 

It is convenient to have the oxalic acid of such a strength that 
1 c.c. of it neutralizes as much Ba(OH) 2 or Ca(OH) 2 as 0*5 c.c. 
of C0 2 . Now 1 c.c. of C0 2 weighs 22x0*0000895 grammes 
= 0*001969 gramme. Oxalic acid crystallizes with 2 molecules of 
H 2 0, its molecular weight is therefore 126, for the formula will 
be (COOH) 2 + 2H 2 0. Therefore in 1 c.c. of the standard 
solution there must be 

1 m 126 _ 0*001969 

-of of — grammes = o # oo28i925 gramme. 

For convenience a stronger solution than this is made by dissolv- 
ing 28*19 grammes of crystallized oxalic acid in a litre of freshly 
boiled distilled water. Each c.c of this will be equivalent to 



ioo ANALYSIS OF AIR 

S cc. of C0 2 ; when the acid is required for use, 10 c.c. of the 
strong acid are diluted with 90 c.c. of distilled water ; 1 c.c. of 
the weak acid then equals 0*5 c.c. C0 2 . 

2. HALDANE'S METHOD 

Haldane has devised a small and portable gas analysis 
apparatus for the estimation of carbon dioxide in air. The 
advantages claimed by it are that the estimation can be completed 
in a few minutes, only a small volume of air is required, and the 
apparatus is easily portable : the disadvantages are the relatively 
large cost, and the difficulty, to the beginner, of manipulation. 
The results obtained by it are sufficiently accurate for practical 
purposes ; the principle on which the analyses are made being 
the absorption of the C0 2 by means of potash. Full details are 
given in text books larger than this, and are supplied also with 
the apparatus itself. 

Detection of Carbon Monoxide in Air 

If CO is present in the air or any mixture of gases in any 
considerable quantity it may be absorbed by a solution of cuprous 
chloride ; if it is only present in minute percentage this method 
is quite useless. 

If a sample of the suspected air be shaken up with a few c.c. 
of a 1 % solution of blood, the latter acquires a pink colour which 
is quite different from the colour of the normal blood. 

Blood thus treated with carbon monoxide gives, in weak 
solution, a characteristic spectrum, showing two well-marked 
bands with sharp edges in the yellow and green parts of the 
spectrum : when the blood is treated with dilute ammonium 
sulphide these bands persist, in contradistinction to oxy- 
haemoglobin, which loses the bands after such reduction. The 
persistence of these two bands after reduction with (NH 4 ) 2 S 
means that carbon-monoxide-haemoglobin is present, and that 
CO was present in the air that was tested. 

Estimation of Carbon Monoxide in Air 

The following account is that of Haldane, who elaborated the 
method : — 

Estimation of the Degree of Saturation of Blood with CO 

" When only a rough quantitative estimate of the percentage 



CARBON MONOXIDE IN AIR 101 

saturation is required, as in ordinary post-mortem examinations 
or in examining the blood of a patient suffering from gas poison- 
ing, all that is necessary is to prepare in three test-tubes of even 
size (i) a solution of normal blood well diluted; (2) some of 
the same solution saturated with coal gas ; and (3) a solution of 
the suspected blood diluted to the same depth of colour as the 
other two solutions. One can then tell roughly by the relative 
pinkness of the suspected blood to what extent it is saturated." 

To measure accurately the extent to which blood is saturated 
with CO he devised the following method: — 

" A solution of about 1 of normal blood to 100 of water is 
made ; also a solution of carmine dissolved with the help of a 
little ammonia, and diluted till its depth of tint is about the same 
as that of the blood solution. Two test-tubes of equal diameter 
(about half an inch) are then selected. Into one of these 5 c.c. 
of the blood solution are measured with a pipette ; into the other 
about an equal quantity is poured. Ordinary lighting gas is then 
allowed to blow into the - second test-tube through a piece of 
rubber tubing for a few seconds. The test-tube is then quickly 
closed with the thumb before the gas has had time to escape, and 
the blood solution thoroughly shaken up with the gas for a few 
seconds. The haemoglobin is thus completely saturated with 
carbonic oxide, and the solution has now the characteristic pink 
tint. The carmine solution, which has a still pinker tint, is now 
added from a burette to the 5 c.c. of normal blood solution in 
the other test-tube until the tints are the same in the two test- 
tubes. Not only, how T ever, must the tints be equal in quality, 
but they must also be sensibly equal in depth. If the carmine 
solution is too strong or too weak, the latter will not be the case, 
and the solution must be diluted or made stronger accordingly. 
It is usually easiest to make the carmine a little too strong at 
first, so that on adding both carmine solution and water equality 
can be established. From the amount of water which required to 
be added it is easy to calculate the extent to which the original 
carmine solution needs to be diluted. The solutions are now 
ready for use, and the actual analysis is made as follows : 5 c.c. 
of the solution of normal blood are measured into one of the 
test-tubes, and a drop of the suspected blood placed in the other 
test-tube and cautiously diluted with water till its depth of tint is 
about equal to that of the normal solution. If carbonic oxide be 
present in the haemoglobin, a difference of quality in the tints of 
the two solutions will now be clearly perceptible. Carmine 



102 ANALYSIS OF AIR 

solution is then added from the burette to the normal blood, and 
water, if necessary, to the abnormal blood, till the tints are equal 
in both quality and depth. The carmine is added by about 
o*2 c.c. at a time, the points being noted at which there is just 
too little and just too much carmine, and the mean being taken. 
The solution of abnormal blood is then saturated with coal gas, 
and the addition of carmine to the other test-tube continued 
until equality is again established, and the amount of carmine 
noted. The percentage saturation with carbonic oxide of the 
abnormal blood can now be easily calculated, since we know how 
much carmine solution its saturation represented as compared 
with what complete saturation represented. 

"The method of calculation is illustrated by the following 
example : To 5 c.c. of normal blood solution, 2-2 c.c. of carmine 
is required to be added to produce the tint of the blood under 
examination, and 6*2 c.c. to produce the tint of the same blood 
fully saturated. In the former case the carmine was in the 
proportion of 2*2 in 7*2 and in the latter of 6*2 in 11*2. The 
percentage saturation (x) of the haemoglobin with carbonic oxide 
is thus given by the following proportion sum :■ — 

6*2 . 2*2 . 

— : — : : ioo : x 

11*2 7*2 

x is therefore = 55*2. As the compound of carbonic oxide and 
haemoglobin is to a slight extent dissociated when the blood is 
diluted with water, the value found is a little too low. The 
corrections needed are as follows : Add 0*5 if 30% saturation be 
found, i-i if 50%, i-6 if 60%, 2-6 if 70%, 4*4 if 80%, io'o if 
90%. Thus, in the above example, we must add 1*3, so that the 
true saturation is 5 6 '5%. In comparing the tints the test-tubes 
should be held up against the light from a window, but bright 
light should be avoided as much as possible, as it increases the 
dissociation. Failing daylight, an incandescent burner with a 
chimney of blue glass and an opal globe may be used as the 
source of light. 

" Haemoglobin brought into intimate contact with air containing 
0-07% of CO will finally reach a state of equilibrium in which it 
is saturated to an equal extent with CO and oxygen. If the 
percentage of CO or oxygen in the air be increased or diminished, 
there will be an exactly corresponding increase or diminution of 
the relative share of the haemoglobin which either gas obtains. 
Air containing 2 xo'0 7 = 0*14% of CO will, for instance, produce 



CARBON MONOXIDE IN AIR 103 

two-thirds saturation with CO, and one-third saturation with 
oxygen, and so on. In the living body the proportion of CO 
taken by the haemoglobin from respired air containing a given 
percentage of CO is not so large as outside the body, about o*i% 
of CO in the air breathed being necessary to produce half satura- 
tion of the haemoglobin. The general law of absorption is, 
however, much the same, and it follows that there is a certain 
maximum of saturation for each percentage. With less than 
°'°5% °f CO in the air this maximum does not exceed 33% 
saturation, and the corresponding symptoms are scarcely appreci- 
able, except on muscular exertion. With more than about 0*2% 
the maximum exceeds 60% saturation. 

" The detection and determination of small percentages of CO 
in air was formerly a matter of great, and often almost insuper- 
able, difficulty. I have recently, however, introduced a simple, 
and I think very satisfactory, method, depending on the already 
described action of CO on blood solution in presence of air. The 
sample of air is collected in a clean and dry bottle of about 4 oz. 
capacity. The cork of the bottle is removed in the laboratory 
under a 0*5% solution of blood, and about 5 c.c. of the 
air allowed to bubble out, a corresponding volume of the blood 
solution entering. The cork is then replaced, covered with a 
cloth to keep off the light, and shaken continuously for about 
ten minutes, when the haemoglobin will have reached the point of 
saturation corresponding to the percentage of CO present. The 
solution is then poured out into a test-tube, and the saturation 
determined with carmine solution in the manner described above. 
It is evident that as in each case the saturation found corresponds 
to a definite percentage of CO in the air, it is easy to calculate 
this percentage. If p be the percentage required, and s the 
percentage saturation found, p is calculated from the following 
formula :— s x . 0? 

P = ~ 

1 00 -s 

Thus, its = 60, p is 0*105. This method may also be used for 
the direct determination of carbonic oxide in lighting gas. The 
latter must, however, be first diluted to T ^ (or with carburetted 
water-gas to T ^) with air. As it is quite easy to make this 
dilution with perfect accuracy, the method is an exact one, and is 
not only rapid, but avoids the difficulties and sources of error 
connected with the ordinary method of determination by cuprous 
chloride, or by explosion." 



104 ANALYSIS OF AIR 



Ozone 



Ozone (0 3 ), an allotropic modification of oxygen, is found in 
the air in the neighbourhood of the sea and after electric 
discharges. 

In order to detect its presence in the atmosphere, a piece of 
blotting-paper is saturated with a solution of KI and starch, and 
exposed to a current of air for from six to twenty-four hours, 
shaded meanwhile from the sun. If ozone is present the paper 
will have acquired a blue tinge from the liberation of iodine 
from the potassium iodide, and subsequent combination of the 
iodine with the starch. 

In the neighbourhood of chemical works the above test is not 
available, since other gases, such as chlorine, will cause the 
appearance of the blue colour. Instead, two strips of neutral 
litmus paper are taken, one of which has been steeped in KI 
solution, and exposed to the air. If ozone is present the litmus 
paper soaked in KI will be turned blue from the conversion of 
the KI into K 2 by the ozone. The control litmus paper is in 
order to ensure the absence of ammonia. 

Noxious Gases in Air 

The air in the neighbourhood of chemical and other works 
frequently contains traces of chlorine, hydrochloric acid, sulphur 
dioxide, and various other gases. These gases when concen- 
trated are certainly harmful ; but when diluted with air, as they 
are usually found, their danger to life is doubtful. The student 
for D.P.H. examinations, however, is expected to be able to 
identify various gases, which are generally supplied to him in 
the undiluted condition. The gases that may be set at such 
examinations are included in the following list : — 



Acid gases. 


Alkaline gases. 


Neutral gases. 


HCl. 


NH 3 . 


H 2 S. 


HNO3. 


(NH 4 ) 2 S. 


cs 2 . 


N 2 3 , etc. 




CO. 


ci 2 . 






S0 2 . 






C0 2 . 







NOXIOUS GASES IN AIR 105 

Method of Procedure 

1. Take the reaction with litmus paper which has been made 

slightly moist. This will give an indication whether the 
gas is acid, alkaline, or neutral. 

2. Smell the gas. Chlorine and hydrochloric acid gas have a 

characteristic odour. So has sulphur dioxide. Ammonia 
and ammonium sulphide are easily distinguished, the 
latter giving, besides the smell of ammonia, the un- 
pleasant odour of rotten eggs. Sulphuretted hydrogen 
also smells like these; and carbon disulphide has the 
odour of concentrated bad cabbages. The oxides of 
nitrogen have their own particular smell, reminiscent of 
strong nitric acid. Carbon monoxide and carbon dioxide 
have no odour. 

With these aids the student will be enabled to diagnose that 
the gas he is examining is, at the most, one of two or three. He 
should now apply confirmatory tests, as follows : — 

Dissolve the gas by shaking in 10 c.c. of water, and test the 
solution. 

HC1. AgN0 3 gives a white precipitate insoluble in HN0 3 , but 

soluble in NH 4 OH. 
HNO3. Brucine test. 

N 2 3 (now HN0 2 ). Metaphenylene-diamine test. 
Cl 2 . Bleaches litmus 'paper. Moist KI paper is blackened by 

the liberation of free iodine. 
S0 2 . Characteristic smell. AgN0 3 gives a white precipitate 

soluble in HN0 3 . 
C0 2 . Lime water or Ba(OH) 2 gives turbidity. 
NH 3 . Nessler's reagent gives a yellow-brown colour. 
(NH 4 ) 2 S. Odour characteristic. Sodium nitro-prusside gives a 

violet colour. 
H 2 S. Lead acetate paper or solution is darkened. 
CS 2 . On burning, sulphur is deposited. 
CO. Characteristic colour and spectrum when shaken with a 

dilute blood solution. 



ANALYSIS OF SOIL 

The chemical and physical examinations of the soil are attended 
by many and great difficulties, and the training necessary to 
become an expert in the subject is both long and laborious. 
Fortunately the examinations which develop upon the hygienist 
are comparatively simple. 

DETERMINATION OF THE SIZE OF THE PARTICLES 

A series of sieves is taken, having meshes of 2 mm., 1 mm., 
and o'5 mm. respectively. 

100 grammes of air-dried soil is taken and broken as finely as 
possible between the finger and thumb. The large pebbles, 
sticks, roots, etc., are removed by hand and weighed. The 
remainder is next transferred to the 2 mm. sieve. After as much 
of the soil is through as will pass, the remainder is again rubbed 
between the finger and thumb in order to break up any cohering 
masses. The amount left on this sieve is then weighed. In a 
similar manner the amount left upon the other sieves, and the 
amount which passes the 0*5 mm. sieve is weighed. The result is 
then tabulated as follows : — 

1. Coarse pebbles, etc., removed by hand. 

2. Pebbles and coarse sand not passing a 2 mm. sieve. 

3. Sand not passing a 1 mm. sieve. 

4. Fine sand not passing a o 5 mm. sieve. 

5. Fine earth passing a 0*5 mm. sieve. 

DETERMINATION OF THE MOISTURE 

Since the moisture-containing property of the soil is chiefly 
possessed by that portion of the soil which passes a 2 mm. sieve, 
5 grammes of such air-dried soil are carefully weighed in a tared 
dish. The dish is then placed in a water oven and heated for 
five hours. It is then transferred to a desiccator, allowed to cool, 
and weighed. The heating, cooling, and weighing are repeated 
at intervals of two hours, until the weight is found to be constant. 
The loss in weight then represents the moisture in 5 grammes. 

106 



THE POROSITY OF A SOIL 107 

DETERMINATION OF THE POROSITY OF A SOIL 

The porosity of a soil depends upon the volume of the solid 
particles as compared with the volume of the interstitial spaces. 
Three factors affect the porosity: (1) the state of divisibility or 
the number of particles per unit volume; (2) the nature and 
arrangement of these particles ; and (3) the interstitial space. 

The porosity is most easily determined by finding the real and 
apparent specific gravity of the soil in question, and dividing the 
latter by the former. 

The real specific gravity is determined by means of a pykno- 
meter having a capacity of 25 or 50 c.c. 10 grammes of soil dried 
at ioo° C. to a constant weight are boiled for a time with a few 
c.c. of distilled water in order to remove any air, and poured into 
the pyknometer. The vessel is rinsed with distilled water, so that 
all the soil is transferred to. the pyknometer. After cooling to the 
requisite temperature, 15° C, distilled water is added to the mark, 
and the whole weighed. The weight of the pyknometer and the 
pyknometer filled to the mark with water being known, the weight 
of the water displaced by the 10 grammes of soil is easily 
obtained. 

Suppose this to be 4791. 

The sp. gr. of the soil is then -=2*08. 

The apparent specific gravity is obtained in the following 
manner : — 

An open cylinder holding 1 litre is taken and filled — small 
quantities at a time — with the soil. As each portion is placed 
in the cylinder, the bottom is struck fairly hard with the palm of 
the hand. When the cylinder is full it is covered with a glass 
plate and weighed. The weight of the cylinder and plate is 
deducted, and the apparent specific gravity thus obtained. 

The real sp. gr. of a sample of soil was found to be 2*64, and the 

. _ o 

apparent sp. gr. 1 '28. The porosity is therefore x 100 = 48*4%. 

2*64 

Schiibler gives the weights of different kinds of soil : — 



lbs. per cu. ft. 
Heavy clay . -75 
Vegetable mould . 78 
Peat . . . 30-50 
The specific gravity thus decreases as the amount of humus 
increases. 



lbs. per cu. ft. 
Sand . . .110 

Sand and clay . 96 

Common arable soil 80-90 



108 ANALYSIS OF SOIL 

ESTIMATION OF CLAY AND SAND 

The constituents of soil are spoken of as sand and clay, the 
sand being the coarser particles which sink rapidly in water, the 
clay being the very fine particles, consisting chiefly of silicate of 
alumina, which remain suspended in still water for a considerable 
time. This is only a rough division, because in any sample of 
soil, every grade can, by appropriate methods, be found between 
particles 3 mm. in diameter and particles o'ooi mm. in diameter. 

In order to estimate the clay and sand, 10 grammes of air-dried 
soil are taken and placed in a beaker which holds about 200 c.c. 
The soil is first moistened with distilled water containing o # oi% 
of NH 4 C1, and about 50 c.c. or 100 c.c. of the distilled water are 
added and the soil well stirred. The soil is allowed to settle for 
five minutes and the supernatant fluid poured into a large clean 
cylinder. 50 c.c. or 100 c.c. more of the water are added, 
the soil well mixed, and again allowed to settle for five minutes, 
when the supernatant fluid is poured off. This is repeated until 
the supernatant fluid is quite clear. 

The sand remaining in the beaker is transferred on to a filter 
and well washed with distilled water, dried, weighed and returned 
as sand. 

The fluid in the cylinder is allowed to stand for from 12 to 24 
hours, when the clay will have settled at the bottom. The whole 
of the upper part of the fluid is filtered through filter-paper 
without disturbing the sediment. When only a thin layer of 
water is left, the clay is stirred up and transferred to the filter- 
paper. The cylinder is well rinsed with distilled water and the 
washings are poured on to the filter-paper. The clay is then well 
washed (at this stage filtration is so slow that frequently two days 
are required to complete the washing), dried, weighed, and 
returned as clay. 

Good loamy soil often contains from 10-15% °f c ^ a Y- Stiff 
soils contain from 20-30%. Sandy soil contains only 1 or 2%, 
and brick clay or kaolin contains 80-95%. 

DETERMINATION OF THE SPECIFIC HEAT OF SOILS 

The specific heat of any substance is the relation between the 
amount of heat required to raise a given mass of the substance 
through a given number of degrees, and the amount of heat 
required to raise the same mass of water through the same 
number of degrees. 



NITRATES IN SOIL 109 

The principle involved in the determination is that a certain 
mass of the soil heated, say, to boiling point when added to 
water at a certain temperature will raise the temperature of the 
water a certain number of degrees, whereas the same mass of 
boiling water will raise the temperature a different number of 
degrees. As the operation is a delicate one and necessitates the 
use of a sensitive calorimeter it hardly lies within the province of 
this book. Suffice it to say that there is a very considerable 
difference in the specific heats of various soils. 

The specific heat varies from 0*19 to 0*51, the latter being a 
peaty soil. Speaking generally, the specific heat increases with 
an increase of humus in the soil. 

ESTIMATION OF THE ORGANIC MATTER 

An approximate estimation of the organic matter in soil may 
be obtained by taking 10 grammes of air-dried soil and heating it 
in a platinum dish at no° C. until a constant weight is obtained. 
The dish is then transferred to an Argand burner and the soil 
oxidized at a low red heat. When the oxidation is complete, the 
dish is transferred to a desiccator, allowed to cool and weighed. 
The loss in weight gives approximately the amount of organic 
matter. 

ESTIMATION OF NITRATES IN SOIL 

In order to estimate the nitrates and nitrites in soil, the 
sample should be spread in a thin layer in an oven having a 
temperature of 5o°-6o° C. in order to prevent any further 
nitrification. 

After the soil is dry, 1000 grammes are finely powdered, 
weighed, and placed in a large flask. 2000 c.c. of distilled 
water are then added, well mixed, and allowed to stand (with 
frequent shaking) for 48 hours. 1000 c.c. are then filtered. A 
small quantity of Na 2 C0 3 is added to the filtrate, which is then 
evaporated to about 100 c.c. 

The nitrates are then estimated by the phenol-sulphonic 
method. 



ANALYSIS OF GROUND AIR 

In order to collect ground air for analysis a convenient method 
is to have a hollow tube furnished with a steel cone. The tube 
is provided at its lower end with perforations, and when it has 
been driven into the ground to the required depth, the upper 
end is connected with an aspirator full of water; the water is 
allowed to flow slowly out. When the necessary amount of gas 
is collected, the apparatus is transferred to the laboratory and the 
gas analysed. 

Ground air contains about the normal amount of nitrogen. 
The C0 2 varies from i% to 8%, and the 2 is correspondingly 
decreased. From time to time NH 3 , H 2 S, CH 4 , etc., are found. 
The methods for the detection of the first two will suggest them- 
selves to the student. CH 4 can only be estimated in a proper 
gas apparatus, which is somewhat expensive, and which requires 
special practice to use. 



no 



DISINFECTANTS 

Certain disinfectants and antiseptics (boric acid, formalin, and 
salicylic acid) have already been discussed in the chapter on milk 
analysis : it remains now to consider other disinfectants that are 
not usually added to food as preservatives, but which are 
employed in public health work in connection with the control 
of infection. A bacteriological standard is here obviously of 
more value than a chemical analysis ; and for the consideration 
of the Rideal- Walker method of standardizing disinfectants the 
student is referred to text-books on bacteriology. 

Occasionally, however, the D.P.H. candidate is asked to identify 
some disinfectant ; and possibly to determine whether the sample 
submitted to him has been adulterated by some inert substance : 
in other words, he is required to estimate the quantity of the 
disinfectant present in the sample. 

BLEACHING POWDER 

ESTIMATION OF AVAILABLE CHLORINE 
Apparatus, etc., required 

i. A flask to hold i litre. 

2. A burette graduated in o*i c.c. 

3. A solution of KI in water. 

4. Freshly prepared starch solution. 

N 

5. — Na 2 S 2 3 , sH 2 (24*8 grammes to the litre). 

6. A porcelain dish. 

The Process 

1. Weigh out 10 grammes of the bleaching powder and transfer 

to the porcelain dish. 

2. Add small quantities of distilled water and mix with the 

bleaching powder until it is thoroughly suspended in the 
liquid. 



ii2 DISINFECTANTS 

3. Transfer the liquid to the litre flask and wash out the dish 

with more distilled water. Transfer this to the litre flask 
and make up to 1 litre with distilled water. 

4. Shake the flask thoroughly. 

5. Measure 20 c.c. of the solution into a dish and dilute with 

about 50 c.c. of distilled water. 

6. Add a drop of acetic acid, and excess of KI to the bleaching 

powder solution in the dish. Free iodine will be liberated 
in proportion to the amount of available chlorine. 

7. Estimate the iodine by means of the decinoriiial thiosulphate 

solution, judging the end point more accurately by the 
addition of some of the starch solution. 

Explanation 

Bleaching powder consists of a number of compounds ; the 
one, however, which gives rise to the available chlorine probably 
has the formula CaOCl 2 . This in contact with water and a 
dilute acid liberates free chlorine. 

CaOCl 2 + H 2 = Ca(OH) 2 + Cl 2 
The chlorine in the presence of KI liberates free iodine. 

2KI + C1 2 = 2KC1 + I 2 
This iodine, and so the chlorine, is estimated directly by the 
decinormal thiosulphate solution. 

Notes 

The thiosulphate solution should be freshly prepared. 
A good bleaching powder will give as much as 33% of available 
chlorine. 

CARBOLIC ACID (PHENOL) 

Qualitative Tests 

1. Ferric chloride gives a deep violet colour with a solution of 

phenol. 

2. Bromine water gives with phenol a white crystalline precipitate 

of tri-bromo-phenol. 

3. KN0 2 and strong H 2 S0 4 gives a brown colour, changing to 

green and blue. 

ESTIMATION OF PHENOL 

TRI-BROMO-PHENOL METHOD 

Apparatus, etc., required 

1. Two stoppered flasks, each of about 150 c.c. capacity. 

2. 500 c.c, flask. 



ESTIMATION OF PHENOL 113 

3. Graduated pipettes — 25 c.c. and 5 c.c. 

4. Solution of KI in water. 

5. Solution of sodium thiosulphate (10 grammes to the litre). 

6. Standard solution of NaBr and NaBr0 3 (1 c.c. =0*0012638 

grammes of phenol). 

7. Starch solution. 

8. Graduated burette. 

The Process 

1. Weigh out 1 gramme of the sample phenol and dissolve in 500 

c.c. of distilled water, to which a trace of NaOH has been 
added to facilitate the solution. 

2. Take 25 c.c. of this solution and transfer to one of the 

stoppered flasks. To the same flask add 25 c.c. of the 
standard bromine solution and 5 c.c. of pure HCL Bro- 
mine will be liberated. 

3. Stopper the flask. 

4. To the control flask add 25 c.c. of the standard bromine 

solution and 5 c.c. of pure HC1. Bromine will be liberated. 
Stopper the flask. 

5. To each flask add excess of the KI solution. The free bromine 

will combine with the KI and iodine will be liberated. 

6. From the burette run the thiosulphate into the control flask 

until the colour has disappeared. Add a little starch 
solution as in the estimation of available chlorine. A few 
c.c. of chloroform added to the contents of the flask 
sharpens the reaction. Note the number of c.c. of thio- 
sulphate used. 

7. Add thiosulphate solution similarly to the flask containing the 

sample phenol, until all the colour is discharged. Note the 
amount of thiosulphate solution used. 

Explanation 

The standard solution containing NaBr and NaBr0 3 liberates 
free bromine on the addition of an acid. 

SNaBr + NaBr0 3 + 6HC1 = 6NaCl + 3H 2 + 3Br 2 

The free bromine thus liberated combines with the phenol 
present to form tri-bromo-phenol. 

The amount of bromine used up by the phenol is represented 
by the difference in the amounts of thiosulphate solution required 
respectively by the control and by the sample solutions. Know- 
ing the amount of bromine used up in converting the phenol 



U4 DISINFECTANTS 

into tri-bromo-phenol, the percentage of phenol actually present 
in the sample can be easily determined. 

EXAMPLE 

The control flask required 20*3 c.c. of thiosulphate solution to 
decolourize its contents. 

The flask containing the sample required 8*6 c.c. of thio- 
sulphate solution. 

.*. the phenol in the sample absorbed bromine corresponding 
to 20*3 -8 6 c.c. of thiosulphate solution, or 11*9 c.c. 

Now 20 *3 c.c. of thiosulphate solution = 25 c.c. of the standard 
bromine solution 

.*. n*9 c.c. of thiosulphate solution = 25 x 11*9 

20-3 
= 14*65 c.c. of standard solution. 

But 1 c.c. of the standard solution = 0*0012638 grammes of 
phenol 

.*. 14*65 c.c. of the standard solution = 0*01851 grammes of 
phenol. 

.*.in 25 c.c. of the sample there were 0*01851 grammes of 
phenol. 

.*. in 500 c.c. of the sample there were 0*37 grammes of 
phenol. 

Therefore in the gramme of the sample of phenol there was 
present but little more than a third of pure phenol. 

Notes 

The flasks should be kept stoppered as much as possible, in 
order to prevent the escape of any bromine vapour. 

The standard bromine solution has the following composition: 
Sodium bromide 8*o grammes, sodium bromate 2*04 grammes. 
Distilled water to 1 litre. 1 c.c. of this solution is equivalent to 
0*0012638 grammes of phenol. 

Potassium or sodium permanganate is used sometimes as a dis- 
infectant. It is easily recognized from its colour. When an 
acid solution of oxalic acid is added the colour disappears. The 
strength of a permanganate solution can be estimated by means 
of decinormal oxalic acid in the presence of H 2 S0 4 . 

Copper sulphate and zinc chloride and salts of iron are used 
occasionally for their disinfecting properties. The detection of 



ESTIMATION OF PHENOL 115 

these metals has already been considered in the section devoted 
to water analysis. 

Sulphites and sulphurous acid are not used on a large scale 
for disinfection except when S0 2 is used for fumigating rooms. 
The smell of S0 2 and of sulphurous acid is characteristic. 

Salicylic acid, boric acid, and formalin have been referred to 
in the chapter on milk analysis. 

Be?izoic acid is too expensive to use on a large scale. It is 
occasionally found in foods. Fe 2 Cl 6 gives a red precipitate. 
When heated with lime benzine is evolved. 

Mercuric chloride and the other salts of mercury have all dis- 
infectant properties. H 2 S gives a black precipitate with mercuric 
solutions, and KOH gives a yellow precipitate of HgO. On 
placing copper foil in a solution of a mercury salt the mercury is 
deposited on the copper. 



MICROSCOPY 

This part of the book deals with the microscopical examination 
of food, clothing, parasites, water sediment, etc., and includes 
descriptions of all the microscopical material about which 
a D.P.H. candidate is likely to be questioned in his examination. 

No pretence is made that this section is a complete treatise on 
such a vast subject as parasitology, and if the student wishes for 
more minute descriptions he is recommended to consult one of 
the many text-books on that science. For the ordinary D.P.H. 
candidate, however, the subject matter in this part of the book 
will be found amply sufficient. 

It is almost impossible to follow a routine plan in the arrange- 
ment of this section ; but, as far as possible, the subjects have 
been kept together : for instance, the parasites of wheat are dealt 
with in connection with wheat, rather than with the other parasites. 

FOOD 

EXAMINATION OF STARCHES 

METHODS OF MOUNTING 

A. In Water 

i . Clean a slide with a handkerchief and see that it is dry. 

2. With a clean platinum loop remove a small quantity of the 

starch to be examined, and place it in the centre of the slide. 

3. Take the slide in one hand, holding it by one end, and tap the 

opposite end against the desk, and remove all the starch 
which does not readily adhere to the slide. 

4. By means of the sterilized loop place three or four loopfuls of 

water in the centre of the slide and mix the starch well. 

5. Breathe on a clean coverslip and whilst the surface is moist 

with the condensed water, gently drop it — moist surface 
downwards — on to the mixture of starch and water. 

6. If the water runs out round the coverslip remove the excess 

with a little filter-paper. The preparation is now ready to 
be examined. 

116 



FOOD 117 



B. In Dilute Iodine Solution 

This method is a very useful one, as the concentric rings can 
very often be seen with great distinctness, even in specimens 
which only show them faintly when mounted in water. 

The process of mounting is identical with that above described, 
a weak solution of iodine being used instead of water. 

The solution of iodine recommended is 

Gram's iodine 1 part. 

Water . . . . . 3 or 4 parts. 

These specimens prepared in either of the above ways will 
only last as long as the water remains. In the warm laboratory 
they very soon dry. For this reason, they should be examined as 
soon as prepared, and if sketches are to be made, they should be 
made at once. 

C. In Farrant's Solution 

Proceed as in A, omitting, however, to breathe on the cover- 
slip. 

Mounted in this way, starches will keep for two or three 
weeks. 

The starch granules possess certain characteristic appearances 
either in their size, shape, concentric rings or hila. These 
appearances enable us to divide them into five groups. 

It is not always easy to differentiate from one another starches 
in the same group ; but not difficult to determine into which 
group a starch should be placed. 



GROUP I 

Wheat, Barley, Rye 

The granules in this group are circular or oval in appearance, 
some being large and others small. They have no very apparent 
hilum and no concentric rings. 

1. Wheat (Tritiacm vulgare). 

2. Barley {Hordeum vulgare). 

3. Rye (Secak cereale). 



n8 MICROSCOPY 








o°o^°o° . °:& 

FIG. 2 FIG. 3 FIG. 4 

WHEAT STARCH BARLEY STARCH RYE STARCH 

X 200 X 200 X 200 

1. The wheat granules are generally very perfect. They are 

chiefly of two sizes, large ones varying in shape from 
circular to oval, and very small ones. Sizes intermediate 
between these are rare. 

2. The granules of barley resemble those of wheat, but (i) the 

large granules are more circular, (2) the number of inter- 
mediate sizes is proportionally much greater, and (3) slight 
indications of concentric rings may be seen. 

3. The granules of rye resemble the two preceding ones, but (1) 

the large granules are larger than either wheat or barley, 
(2) the large, intermediate, and small granules are more 
nearly equal in number, (3) the granules are more frequently 
cracked and occasionally show a stellate hilum but no con- 
centric rings. 

GROUP II 

Potato, Arrowroot 

The granules of this group are large and oval, and show a 
distinct hilum and well-marked concentric rings. 

1. Potato {Solatium tuberosum). 

2. Arrowroot (Maranta arundinacea). 

1. The potato granules have the hilum as a point at the narrow 

end. 

2. The arrowroot granules, on the other hand, have a punctate 

or linear hilum at the broad end. 



FOOD 
Note 



119 



Although it is not true that every potato granule has the 
hilum at the narrow end, or is even oviform ; or that every 





FIG. 5. POTATO STARCH 
X 200 



FIG. 6. ARROWROOT STARCH 
X 200 



arrowroot granule has the hilum at the broad end ; the majority 
of the granules in any pure specimen agree with this description. 
It would be obviously impossible to differentiate between one 
oval potato and one oval arrowroot granule. 

GROUP III 
Pea, Bean, Maize 

The granules of this group are round or oval without any 
evident rings, but with linear or stellate hila. 

1. Pea {Pit sum sativum), 

2. Bean (Faba vulgaris). 

3. Maize (Lea mays). 



e 



\ 










® 









FIG. 7. PEA STARCH FIG. 8. BEAN STARCH FIG. 9. MAIZE STARCH 

X 200 X 200 X 200 

1. The pea granules are generally a long oval in shape, fairly 
large, but showing different sizes. They generally present a 
linear hilum, but this is sometimes branched. 



120 MICROSCOPY 

2. The bean granules are of a shorter oval than those of the pea, 

and are more uniform in size. The hilum is linear, but 
more often branched (sometimes even stellate) than in the 
case of pea granules. 

3. The maize granules are mostly polyhedral in shape — approxi- 

mating to the oval form. They are often cracked, and 
present a well-marked stellate hilum. 



GROUP IV 

Rice, Oats 

The granules of this group are much smaller than those of the 
preceding groups. They are angular, and appear to be faceted. 

1. Rice (Oryza sativa). 

2. Oat {Avena sativa). 

1. The rice granules are the Q ^ 

smallest of all those with n ^ q O 

which we are dealing. Under \J q 

a higher power an eccentric r;"^/^ 

hilum may sometimes be /^^^'y^\ 

made out. The granules \^^o^ 

are often massed together * ^ ^" 

in angular and irregular FIG * I0 FIG - IX 

, ° & RICE STARCH OAT STARCH 

shapes. x 200 x 200 

2. The oat granules are larger 

than those of rice, and hila are not to be found. These 
granules are found in masses, but the contour is generally 
regular and oval, and not irregular and angular. 



GROUP V 

Sago, Tapioca 

The granules of this group are very irregular in shape, and 
many appear truncated. They have a hilum and badly denned 
rings. 

1. Sago (Sagus farinifera). 

2. Tapioca {Jatropha manihoi). 




ANIMAL PARASITES 



121 



The sago granules are large 
and irregular. They are 
often rounded at one end 
and truncated at the other. 
The hilum is frequently 
rounded. 

The tapioca granules are 
much smaller than those 
of sago, but are in other 
respects similar. 







G-*jrS 



FIG. 12 
SAGO STARCH 

X 200 



FIG. 13 

TAPIOCA STARCH 

X 200 



The Parasites of Grain, Flour, etc. 

Various parasites are found affecting grains, flours, and bread. 
Some of these parasites are harmless, others are somewhat 
injurious when consumed. 

They may be divided into two classes : — 

1. Animal. 

2. Vegetable. 

I. ANIMAL PARASITES 

a. Corn weevil {Calandra granaria). 

b. Meal mite (Acarus farince). 

c. Pea bruchus {Bruchus pisi). 

d. Ear cockle (Tylenchus tritici). 

a. The Calandra granaria is one of many allied species of 
insect which affect grain. 

The corn weevils belong to the order 
of Beetles (Coleoptera). Two species are 
well known in England, the Calandra 
granaria (or Sitophilus granarius) and 

the Sitophilus 
oryzce. 

The insect 
perforates the shell and abstracts the 
contents of the seed, leaving merely 
the coverings. All the harm this in- 
sect does, therefore, is simply to eat 
the flour ; it does not of course affect 
any grains which are not attacked, 
x 100. {adnat. t.g.s.) nor is it ground up with the flour as 





FIG. 14 

CALANDRA GRANARIA 

X 4 



122 



MICROSCOPY 



in the case of some of the parasites. The grains are attacked 
when the corn is actually standing. 

b. Acarus fan rice. This is also an insect which is frequently 
found in inferior and damp meal, flour, etc. 

It bears some resemblance to the Acarus scabei, but a close examination 
will reveal the great difference between the bodies and legs. The body of the 
Acarus scabei is much rounder than that of the faring, and the legs of the 
meal mite are fairly thick up to the extremity, whilst those of the Acarus 
scabei are thick at the proximal, but quite thin at the distal end. 




c. The Bruchus pi si. The Bruchus pisi (the pea bruchus), 
Brnchus rufimaniis (bean bruchus), and the Bruchus gra?iarius 
(the grain bruchus) belong to the same 
order (Coleoptera) as the weevils, which 
they resemble in their main features. The 
first two, as their names imply, are con- 
nected with peas and beans. The adult 
female lays her eggs in the young fruit, and 
the larvae live in the seeds, eating up all 
the internal parts and changing to pupae 

FIG. 16. BRUCHUS PISI w j thin tfae outer shdL 

d. The Tylenchus tn'tici ( Vibrio tritici). 

The worms seen when the contents of an infected grain are 
examined under the microscope 
are the larval forms of a nema- 
tode worm. 

In the ears of wheat affected 
by this worm the grains are mis- 
shapen, blackish, and consist of 
a thick hard scale enclosing a 
white powdery substance, com- 
posed almost entirely of the 
larval forms of the worm. 

In order to examine this 
powder under the microscope, 
it is only necessary to place a 
little on a clean slide and to 
mount it in water. 

Permanent specimens may be 
prepared by mounting in Farrant's solution, the powder may be 
thoroughly dehydrated by drying or by treatment with alcohol 
and xylol, and mounted in Canada balsam. Very pretty -sped- 




^^^^^^ 



FIG. 17. TYLENCHUS TRITICI 
X 60. (adnat. T.G.S.) 



VEGETABLE PARASITES 



123 



mens may be prepared by staining the worms with eosin and 
mounting in Canada balsam, in the usual manner. 

If the infected grain be sown in ordinary moist ground, the 
husk simply rots. The larvae escape and become active. They 
move along the ground in search of growing blades of corn. 
When they find one, they slowly creep up and eventually reach 
the young soft grain, which they penetrate. Here they form gall- 
like swellings, in the middle of which they are found. 

In this position they quickly develop into the adult form. 
After fertilization by the males, the females lay a large number of 
eggs, and both males and females die. The eggs subsequently 
hatch and the larvae are seen. 

Closely allied to this worm is the Anguillula aceti, which is 
sometimes found in vinegar, when this is made from beer or wine, 
and which is also found in sour paste. 

II. VEGETABLE PARASITES 

a. Pe?iicillium glaucum. 

b. Aspergillus glaucus, albus, etc. 

c. Mucor. 

d. Peronosporon. 

e. Puccinia graminis and Rubigo vera (rust). 
/ Ustilago segetum (smut). 

g. Tilletia caries (bunt, Uredo fcetida, Ustilago carbd). 
h. Claviceps purpurea (ergot). 

a. The Penicillium glaucum is a common mould, found very 
extensively in the air. It is frequently 
found forming a greenish growth, on 
damp grain, flour, bread, or cheese. 

This mould resembles the others in 
consisting of many long threads (hyphae) 
often interlaced and forming a mycelium. 
The hyphae branch and produce special 
spore-bearing ones. The end of this last 
hypha then branches into three or more 
terminal filaments which in their turn 
divide transversely to the long axis. The 
protoplasm of these short rods now be- 
comes differentiated and round or oval 
spores with thick cell walls are found. 
These soon separate from one another, FIG# jg 

and free spores are found. penicillium glaucum 

X 100 




124 



MICROSCOPY 



b. Aspergillus glaucus, etc. This species of mould is also 
found in damp grain, etc. It resembles the penicillium 
in its mode of growth, but differs from it in the way 
in which the spores are formed. The end of the 
spore-bearing hypha becomes enlarged and the spores 
appear to grow out of the bulbous end, and are at 
first attached to it by fine pedicles. Generally there 
are two or three rows of spores on each head, the 
pedicles of the external row being longer than those 
of the other rows. When the spores are ripe they 
simply fall off, and so become free. 

c. Mucor. This form of mould is found in similar 
positions to the last two. It resembles these in its 
mode of growth except that it forms its spores in still 
another way. The end of the spore-bearing hypha 
becomes enlarged, and instead of the spores growing 
out from this enlargement, as in the case of the 
aspergillus, the end attains a considerable size (quite visible to 
the naked eye). The protoplasm within the wall of the head 




fig. 19 

ASPERGILLUS 
X IOO 

(After Howes) 




m 



fig. 20. Mucor : (a) special spore-bearing hyphae ; (5) head x 100, 
showing internal spores ; [c) and (d) conjugation. (After Howes) 

undergoes differentiation, and the spores are formed by this means 
inside the envelope which surrounds the head. When the spores 
are ripe the envelope is ruptured, and the spores set free. 



VEGETABLE PARASITES 



125 



N 




This mould is occasionally found to multiply by a process of 
conjugation, as shown in the diagram. The swelling so formed 
is found to become differentiated in a manner similar to that 
found in the head produced on a hypha. 

d. Peronospora. These moulds do not affect the prepared 
product so much as the living plant. They 
were the cause of the great Irish potato 
famine, and are found affecting many of 
the " root " crops as onions, parsnips, 
turnips, etc. 

The mould first affects the leaves and 
gradually travels downwards until finally 
the tuber or root is affected. 

The growth consists of a dense mycelium 
which produces spore-bearing hyphie ex- 
ternally. 

These hyphae frequently branch, some- 
times many times. At the end of each 
branch a single spore is produced. This 
when it is ripe separates and so becomes 
free. 

e. Puccinia graminis. This parasite FIG - 2I - peronosporon 

r j a- j." • a.' r X 100. (After Vines) 

is found affecting many varieties of corn. 

The process of infection is as follows : A spore becomes attached 
to the, say, wheat grain, and as it grows, it sends free filaments 
into the interior of the grain. As time goes on minute trans- 
parent cellules are developed from the mycelium : these enlarge 
and become coloured. As the result of their increase in size, 

the cuticle first becomes distended, 
and finally ruptures, and the spores 
are found at the surface as rust. 

The distinctive features of the 
Puccinia are the uniseptate or 
double spores, which are attached 
on a distinct peduncle, and it is 
in this condition that the parasite 
is shown at the various examin- 
ations. 

/ Ustilago segetum (syn. 
Uredo segetum, smut). This — a 
common parasite of corn — is one of a large family of parasites 
which are found affecting plants. 





"^a^sgss 



Fig. 22 
spores of puccinia graminis 
x 350 



126 



MICROSCOPY 




Among the standing corn withered heads are often 
seen, which appear black or brown. If they are rubbed, 
or even touched, a fine brownish powder falls off. This 
powder consists of the spores of the parasite. 

Under the microscope these are seen to be small 

spherical spores, which are generally coloured a light 

brown. They are entirely free, as by the time the 

spores are ripe the mycelium will have disappeared. 

g. Tilletia caries (syn. Uredo fatida, Ustilago carbo, bunt). 

This is another member of the ustilaginre, to which order the 

Ustilago segetum belongs. 

The parasite is found in the interior of the grain, but does 
not affect its external appearance, or if it does only by slightly 
darkening it. In fact it is often stored with the sound grain, and 
it is not until the corn is ground that its presence is determined. 

If an affected grain be cut or broken open, the interior is seen 
to be filled with a sooty, rather fetid powder. When this powder 
is rubbed between the fingers it has a greasy feel. 

Under the microscope these spores are seen to be brownish 
spherical bodies with a reticulated surface. They are generally 
free, but some are found with part of the attached hyphae, and 
sometimes two or three are seen to be joined together by hyphae. 







FIG. 24. TILLETIA CARIES 
X 200. {ad not. T.G.S.) 



FIG. 25. TILLETIA CARIES 
X 500. {ad fiat. T.G.S.) 



h. Glauiceps purpurea. This fungus is found chiefly affect- 
ing rye, and the mycelial growth — termed the sclerotium — which 
replaces the actual grain is known as ergot. In the spring time 
of the year small hair-like growths with a bulb at the end grow 
out from the mycelium. These are known as stromata, and each 
contains near its border a row of receptacles (ascocarps), contain- 
ing oval-shaped bodies known as asci. These ascocarps and the 



MILK 



127 



contained asci are the preparations of ergot usually shown at the 
examinations. 

CLAVICEPS PURPUREA 
(ergot of rye) 





FIG. 26. SCLEROTIUM 

WITH STROMATA 

(Nat. size) 



FIG. 27. SECTION OF THE END OF A 

STROMA, SHOWING ASCOCARPS AND ASCI 

X 80. (Photo) 

MILK 



The microscopical examination of milk, apart from bacterio- 
logical considerations, is not of great value in hygiene. Pure 
normal milk when viewed with the microscope is seen to consist 
almost entirely of fat globules, which vary only slightly in size. 
The globules are all small, the largest being about three times 
the size of the smallest. In many samples of pure milk cellular 
elements are absent or rare ; but in others obtained from un- 
doubtedly pure sources " leucocytes " may be present, sometimes 
in large numbers. These leucocytes closely resemble poly- 
morphonuclear leucocytes, but differ from them in slight respects : 
their presence alone is not sufficient to condemn a milk sample. 
If, however, typical polymorphonuclear leucocytes are seen, 
accompanied by pyogenic organisms, the milk may be from a 
cow suffering from mastitis and then will be unfitted for human 
consumption. 

Gross dirt, such as manure, hairs, shreds of clothing, etc., will 
also render a milk sample unfit to drink ; and shows neglect on 
the part of the provider to filter the milk before it was dis- 
tributed. 



128 



MICROSCOPY 



BUTTER AND MARGARINE 

Although the microscopic examination of butter and margarine 
is not so important as the chemical examination, pure butter 
differs very markedly from margarine. 

In order to examine these substances, a small quantity of the 
butter or margarine should be spread in a thin layer on a clean 
slide. A drop of i% osmic acid in water should then be placed 





FIG. 28. BUTTER 
X 400. (adnat. T.G.S.) 



FIG. 29. MARGARINE 
X400. {adnat. T.G.S.) 



on the fat and a clean coverslip superimposed. The osmic acid 
serves to show the contour of the globules very clearly. 

In the case of pure butter it will be seen that the globules are 
small and do not vary much in size. The largest globules are not 
more than four or five times the size of the smaller ones. 

The globules of margarine vary greatly in size, the largest being 
fifteen to twenty times as large as the smallest ones. 

COFFEE 

Coffee is obtained from the seeds of the Caffea Arabica. For 
use it is ground and generally mixed with a modicum of chicory, 
varying from 10 to 90%. So long as such a mixture is sold as a 
mixture there is no infringement of either law or honesty. It 
sometimes happens, however, that a mixture of ground coffee and 
chicory is sold as pure coffee. In order to detect this fraud it is 
necessary to be able to identify the two substances. 

In order to examine them under the microscope the ground 
substances should be warmed in a watchglass containing 40% 



COFFEE 



129 



soda solution, and mounted in water or soda. Unless this is 
done it will be found that the grains are so hard and coarse that 
it will be impossible to mount them satisfactorily. The soda will 




FIG. 30. MEMBRANE OF COFFEE BERRY, SHOWING SPINDLE CELLS 
X 100. {ad nat. T.G.S.) 

take some of the colour out of the grains, but this will be found 
an advantage rather than a disadvantage. 

Under the microscope the endosperm cells form the main bulk 





fig. 31 fig. 32 

DOTTED VESSELS OF CHICORY LACTEAL VESSELS OF CHICORY 
X 100. (After Moller) x 100. (After Moller) 

9 



130 



MICROSCOPY 



of the preparation. These are knotted, thickened, thick-edged 
and polygonal, and may contain remnants of the original con- 
tents. Here and there will be found remnants of the membrane 
lining the berry. This membrane has attached to it a number of 
very characteristic spindle-shaped cells. 

Chicory consists of the ground dried root and contains 
elements quite foreign to the coffee berry. The parenchyma is 
much more open than the endosperm cells, and both lacteal 
vessels and the dotted ducts are numerous. 

Numerous other adulterants are from time to time added to 
coffee, such as various starches or starch-containing tissues, which 
are obvious upon microscopic examination. 

TEA 

Tea consists of the dried leaves of the Camellia thea^ of which 
there are several varieties. 

In order to examine the leaves they should be soaked in water, 





loooooooa ca 



fig. 34 

SECTION OF TEA LEAF, SHOWING IDIOBLASTS 
X 160. (After Moller) 



FIG. 33. TEA LEAF 
x 4. {adnat. T.G.S.) 



COCOA 



131 



and when they have assumed their original shape they may be 
dried between blotting-paper and mounted on glass in formalin- 
gelatin or other like substances. 

The leaf thus prepared is seen to be elliptical in shape. The 
margin is serrated and the apex of each serration is surmounted 
with a minute spine. These serrations do not extend quite to 
the point of attachment of the stalk. The apex of the leaf is 
slightly emarginate. The ribs come off from the midrib nearly 
dichotomously and form a looped network which extends nearly 
but not quite to the edge of the leaf, leaving a clear margin. 

If there is any doubt from the shape of the leaf as to its 
genuineness, a small portion should be cut off near a rib, warmed 
in a 20% solution of soda and mounted on a slide, the coverslip 
pressed down firmly but gently. Upon examining the specimen 
under the microscope long tough tenacious branched cells are 
seen. These are termed idioblasts, and do not occur in any of 
the leaves likely to be mistaken for tea leaves. 

COCOA 

Cocoa is prepared from the roasted seeds of the Theobroma 
cacao. If the cocoa nibs be finely ground in a mortar and 
mounted in water, it will be found that there is so much fat 




pig. 35 

(a) Parenchymatous cells of the cocoa bean 

x 150 

(b) Portion of husk, showing characteristic cellular hairs 
X 150. (After Rubner) 

present that the tissues will be seen with difficulty. In order to 
avoid this the ground nibs may be treated with ether and subse- 
quently with warm water, and mounted in water. 



132 MICROSCOPY 

A second method is to warm some of the ground nibs in a 
watchglass containing a little 20% soda. Some pieces are then 
mounted in soda. If, as sometimes happens, the particles are 
not sufficiently soft to allow the coverslips to be pressed down 
on to the specimen they may be crushed between two slides 
before mounting. 

Two kinds of tissue will be seen upon microscopic examina- 
tion, one the external covering and the other the parenchyma. 
The cells of the external covering are large and have super- 
imposed "hairs" consisting of thick-walled cells arranged as in 
the illustration. The parenchyma consists of smaller mucilage 
cells, some of which contain starch granules and others the 
pigment of the cocoa. 

The most of the prepared cocoas consist only of the paren- 
chymatous cells, with or without the addition of other starch, 
and generally with a portion of the fat removed. 

Cocoa starch granules are about the same size as rice, but are 
rounded in contour. 

The addition of foreign starches may be easily ascertained by 
shaking up some of the cocoa in cold water, allowing the coarser 
particles to settle, and mounting some of the milky supernatant 
fluid. 

CLOTHING, ETC. 

Under this heading are included the fibres used in the manu- 
facture of clothing ; and those which are in common use for 
other purposes. They may be found in water sediments, milk, 
sewage and elsewhere; and their identification is frequently 
required of the student at D.P.H. examinations. 

A. VEGETABLE FIBRES 

EXAMINATION 

All the vegetable fibres may be examined under the microscope 
in water. 

The fibres should be macerated in water in order to get rid of 
the air, and teased out as finely as possible. They may then be 
placed on a slide with some water, and a coverslip superimposed. 
The excess of water at the edges of the coverslip should be 
removed with blotting-paper previous to examination. 

Permanent specimens may be made either stained or unstained. 
The fibres may be coloured with any of the aniline dyes in weak 
solution, for a few minutes. 



CLOTHING 



133 



After staining, or if they are to be mounted unstained, they 
should be immersed in absolute alcohol for several minutes, then 
removed to xylol for 4 or 5 minutes, drained of the excess of 
xylol and mounted in Canada balsam. 

1. Cotton 

This is the downy hair of the seeds of plants belonging to the 
family Gossypium. Four species appear to be available for this 
purpose, the commonest being the Gossypium barbadense. 

Under the microscope the 
fibres are seen to be long (from 
I to 1 in.) and thin, the diameter 
being about 20 or 30 /x. They 
are flattened and have a very 
distinct margin which sometimes 
gives the impression of a double 
contour. The chief characterstic 
about the fibres is that they are 
all twisted, and this, however 
short the fibres may be. 

Cotton fibre is largely used in 
the manufacture of sheeting, 
calico, towelling, fustian, vel- 
veteen, flannelette, paper, etc. 
Mixed with wool it constitutes 
merino, which is used for vests, 




Fig. 36. cotton fibres 

X 100. (aduat. T.G.S.) 



socks, etc. It is used as an adulterant of silk, but not to such a 
great extent as is jute. 



2. 



Linen Fibre— Flax 



Flax consists of bast fibres and is obtained from the stalk of 
Linum usitatissimum. The stalks are allowed to rot on the 




FIG. 37. LINEN FIBRES 
X 100. {ad. not. T.G.S.) 



134 



MICROSCOPY 



ground and are subsequently beaten and combed, the result of 
the process being the raw flax of commerce. 

Under the microscope the fibres are about the same diameter 
as cotton, but are cylindrical (not flat). At more or less regular 
intervals there are distinct nodes or transverse divisions, and 
from some of these fine hairs (a few /x long) are seen to issue. 

Flax is used for shirts, collars, sheeting, and rags made of 
linen are used to make paper of good quality. 

3- Jute 

Jute is the bast fibre of the Corchorus capsularis or Corchorus 
olitoriuS) a tropical shrub grown chiefly in Bengal. Microscopi- 
cally the fibres are seen to be cylindrical and to have a central 
channel which varies in width and is very distinct. Jute is used 
for making mats and sacking, and in this country is used largely 
as an adulterant of silk. 

4- Hemp 

Hemp consists of the bast fibres of the Cannabis sativa and 
resembles linen very closely. It is coarser than linen, however, 
and may generally be identified by this character. 

It is used chiefly for the manufacture of sacking and ropes, and 
is little seen as an article of clothing. 




fig. 38. JUTE 

100. {ad nat. T.G.S.) 



39. MANILLA HEMP 

100. {ad nat. T.G.S.) 



CLOTHING 



i3S 




FIG. 40. WOOD FIBRES 



5. Coir 

Coir is the coarse fibre obtained from the outer husk of the 
cocoanut. Under the microscope the fibres are seen to be very 
coarse and irregular. 

It is used chiefly in the manufacture of mats and coarse ropes, 
and rarely if ever is met with in clothing in this country. 

Paper 

Paper which is sometimes 
found in the sediment of water 
and which has been macerated 
is seen to consist either of linen 
or cotton fibres, or of wood 
fibres. Many toilet' papers 
are made from wood pulp. 
This paper macerated in 
water and examined under the 
microscope is seen to consist 
of fibres, many of which show 
"spiral cells" (A) and other 
"pitted ducts" (B). x 100 

B. ANIMAL FIBRES 

The following are best examined by macerating for a short 
time in dilute soda (2-5%) and mounting in water or dilute soda. 

Note 

The soda should not be used too strong nor for too long 
a period, since wool and hair are eventually disintegrated and 
dissolved by it. 

1. Wool 

Wool is the prepared fleece 
from sheep and goats. The 
wool used in some Jaeger 
material is derived from the 
camel. 

Under the microscope the 
fibres are seen to be cylin- 
drical and to be thicker than 
cotton or linen. The chief 
characteristic of wool is the 

FIG. 41. WOOL FIBRES 
X 100. (ad nat. T.G.S.) 




136 



MICROSCOPY 



imbrication of the external scales, which gives the edge a ser- 
rated appearance. 

Wool is used in making flannel, blankets, worsted stockings, 
underclothing, etc. 

2. Silk 

Silk is the fibre produced by the larvae of several kinds of 

moth, the Bonibyx mori^ the 
Antherea yamamaya, Antherea 
Pernyi, and Attacus cytithia, to 
serve as a sheath for the chrysa- 
lis until it emerges therefrom as 
the adult moth. 

If silk be mounted in water 
and examined under the micro- 
scope it is seen to be quite 
structureless and waxy. In reality 
there is a central core surrounded 
by albuminous material. The 
fibres are smaller than any of 
the preceding, the diameter being 
half or less than half that of 
wool. There are no nodes, im- 
bricated scales, or twists. 

It is dissolved by strong alkalis and acids, even by acetic acid. 




FIG. 42. SILK FIBRES 
X 100. (adnat. T.G.S.) 



HUMAN PARASITES 

Under this heading are considered some of the common 
parasites that infect the body and clothing of man. Internal 
parasites such as the worms and bacteria do not, for the most 
part, come within the scope of this book ; but mention is made, 
under the section devoted to meat inspection, of certain of the 
parasitic worms which are introduced to the body through the 
ingestion of infected meat. At present, however, only those 
common external parasites, likely to be placed before an exami- 
nation candidate, are considered. 



A. INSECTA 

The Pulex im'tans (the common human flea) does not 
require much description. There are many species of fleas ; and, 



HUMAN PARASITES 



137 



although man is susceptible to the attacks of those which normally 
affect the lower animals, these insects prefer for the most part 
their own particular host. 

Fleas resemble flies to some extent ; but they have only single 
eyes and extremely rudimentary wings. A flea is provided with 
a proboscis for piercing and sucking. 





FIG. 43. PULEX IRRITANS 
X 10. (After Beille) 



FIG. 44. PULEX PENETRANS 
X 10. (After Beille) 



The female lays her dozen eggs about the floors of houses, 
kennels, etc. Six days in the summer suffice for the appearance 
of the worm-like larvae, which are provided with a powerful biting 
mouth. They live on particles of decaying organic matter. They 
move about by means of the hooks and hairs which are placed 
on the posterior border of each of the thirteen rings which they 
possess. At the end of 1 1 days the larva spins a cocoon and is 
transformed into a chrysalis; in another 10 or n days the 
chrysalis emerges as the perfect insect. 

The Sarcopsylla penetrans (chigoe) is nearly allied to the 
last described and has a familiar history. 

The adult female gets from the ground generally on to the 
foot. Here she burrows her way beneath the skin, holding on 
with her powerful mandibles. Soon after she has become para- 
sitic she swells up to twice or three times her normal size 
with eggs. 

The Gimex lectularius (bed bug) is a small insect, having a 
mouth in the shape of a beak or rostrum, adapted both for piercing 
and sucking. 

The adult female lays about 50 white cylindrical eggs in that 
period of the year between March and September. The eggs 
have a hinged lid, and after five or six days of incubation, the 
young cimex opens the lid and walks out. The young do 



138 



MICROSCOPY 



\y 




fig. 45 
cimex lectularius 

X 10. {adnat. T.G.S.) 

hooks for attachment. 



not come to maturity for 10 or n months, and during their 
adolescence undergo three or four moultings. The young are 
more slender than the adults and have less colour. 

The cimex lectularius is wingless : it 
prefers darkness rather than light, and lives 
in corners and niches. In the twilight it 
comes out of its corner and searches for 
its food until the morning, retreating when 
the room grows light. The young cimex 
is able to hunt for itself and is independent 
of the adults. 

The odour associated with these insects 
is due to glands situated in the first seg- 
ment of the abdomen — the adult bearing 
two, and the young three. 

The Pedictlli are provided with pierc- 
ing and suctorial mouth parts. The mouth 
consists of a soft retractile beak, conical in 
shape, and furnished below with a row of 
Inside the soft beak are four grooved plates 
which when juxtaposed form a membranous tube which can be 
extended beyond the mouth, and which is used for piercing. 
The thorax is small in comparison with the size of the abdomen, 
and is not distinctly divided into segments, although as in all 
insects the three pairs of legs are all attached to it. 

The Pediculus capitis, as its name implies, is chiefly found on 
the hairy scalp and obtains its food by piercing the skin and 
sucking the blood. It is of yellowish brown colour, 
which is darker at the edges. The legs have a spine 
at the extremity which can be opposed to the end of 
the digit. This enables the insect to suspend itself. 

The female lays about 50 greyish eggs which are 
covered at the end with a hinged lid. The eggs are 
fastened on to the hair with chitinous material and 
the hair is constricted at this spot. They are nearly 
always fastened on the hair near the scalp, so that 
those found an inch or so from the stem are generally 
empty — the young having been hatched. 

The eggs are hatched in about a week and the 
young pediculus opens the lid and crawls out. The 
young resemble the adults except in size, and undergo 
no moulting as in the case of the cimex. In three 




HUMAN PARASITES 



139 




weeks or a month they are full grown and are able to re- 
produce. 

The Pedi cuius uestimentorum or body 

louse is the same length as the head louse, 

but is about twice as broad. The colour is 

the same as that of the head louse, but is 

not darker at the edges. The head is more 

triangular in shape than that of the head 

louse. In other respects the resemblance is 

almost exact. 

The female lays her eggs, to the number 

of 70 or 80, in the folds of the clothing, FIG . 47 . PE diculus 

where the pediculus lives — only coming on vestimentorum 

to the body to feed. These eggs hatch in x IO - ( After Beille > 

about a fortnight or three weeks and the 

young pediculus is adult in another fortnight and prepares for 

egg laying. # 

The Pediculus pubis differs greatly in shape from the preceding 

species, It is almost triangular and 
the abdomen is less broad than the 
thorax. Between the two there is no 
constriction. Each leg carries at its 
free extremity a definite claw, and 
not merely a spine, but it is with the 
posterior pairs that the insect hooks 
itself to the hairs. 

The female lays 10 or 12 eggs, 
w T hich she attaches to the hair quite 
at the base. The development of 
the egg resembles that of the pre- 
ceding exactly. 




PEDICULUS PUBIS 
X 20. (After Beille) 



B. ARACHNIDA 

To this class belong several forms of acari which are met with 
as human parasites. The acari as a class differ from the true 
insect in several respects. There is no sign of division between 
the abdomen and thoracic portions, nor is the abdomen seg- 
mented ; some of the legs are attached to the anterior, and the 
rest to the posterior portion of the body. 

The Sarcoptes SCabei (Acarus scabei) has an oval body 
bearing four pairs of legs, two pairs placed anteriorly and two 



140 



MICROSCOPY 




FIG. 49. ACARUS SCABEI 
X 60. (Semi-diagrammatic) 



postero-laterally on the under surface. The two front pairs 
terminate in small suckers and the posterior pairs in spines. 
The animal is greyish in colour and semi-transparent. It carries 

several pairs of hairs, the longest pairs 
being on each side of the anus. 

The female alone forms the burrows 
which are characteristic of scabies ; 
she lays about 15 ovoid eggs in the 
bottom of the tunnel. In about six days 
these are hatched. They resemble the 
adult in general shape, but they are 
completely asexual; they carry only 
three pairs of legs, two anteriorly and 
one pair posteriorly. In order to gain 
their liberty they pierce the vault of 
the tunnel, and so arrive on the skin. 
In this stage the larva undergoes two 
or three separate moults. In the next 
stage it obtains its fourth pair of legs, 
and those which subsequently develop into females are somewhat 
larger than those that become males. After the next moult the 
sex of the young is determined and the females are considerably 
larger than the males. 

The male is now adult and undergoes no further change. The 
adult female again moults before she makes her burrow and lays 
her eggs. The male is more agile than the female and only 
excavates the skin sufficiently to find a lodging, where he may 
be seen as a little brown speck. 

The intolerable itching which the presence of the females in 
the tunnels produces is probably due to the secretion by the 
acarus of a poisonous fluid. This is only secreted during the 
night and accounts for the usual phenomenon that the itching is 
only noticed when the patient is in bed. 

The tunnels are found chiefly about the hands, genitals, 
buttocks and thighs, but may be found everywhere except on 
the back of the head. 

In order to obtain an acarus, the tunnel should be torn 
up with a sharp needle, and the female picked up on its 
point. 

To examine it, it may simply be mounted in water, or in 5% 
potash. 

Similar acari affect horses, cattle, cats, etc., and these are 



WATER SEDIMENT 



141 



occasionally found parasitic on human beings, but they prefer 
their normal hosts. 

The ticks or Ixodes, of which the common sheep tick {Ixodes 
nanus) is perhaps the best-known member, are commonly dis- 
tributed in nature, and are occasionally parasitic on man. 

They differ from the sarcopsidae in having all four limbs at 
the anterior extremity, and are armed with a powerful beak. 




a 

FIG. 50. IXODES RICINUS 
X 3 {a) Dorsal view ; (3) Ventral view. (After Beille) 



The female alone obtains her nourishment from the animal 
upon which she is parasitic, the larvae and males being only 
accidental parasites. 

The female grips the hair or skin with the legs and digs her 
beak through the skin at right angles. There she remains for 
several days until she is full of blood. She then withdraws her 
beak and drops off to the ground. If she is brushed off whilst 
she is sucking, her beak is left in situ and may be a source of 
irritation. The larvae have a similar life-history to that of the 
Sarcopsidae. 

WATER SEDIMENT 

The following classification comprises the substances that may 
be found in examining a water sediment : — 

A. Mineral matter, sand, clay, etc. 

B. Vegetable matter. 



Diatomaceae. 
Schizophyceae. 



Schizomycetes. 
Cyanophyceae. 



142 



Algae. 
Fungi. 



MICROSCOPY 



Chlorophylaceae. 



Various more complex plants, or their debris. 
C. Animal matter. 
Protozoa. 
Crustacea. 
Spongidia. 
A arious more complex animals, or their debris. 




FIG. 51. DIATOMS 
X 200 

a, surface view ; b, side view, 
showing two halves of frustule 




FIG. 52. DESMIDS 
X 200 




FIG. 53, VORTICELLA 

X 150 




FIG. 54. EUGLENA VIRIDIS 
X 300. (After Ehrenberg) 




FIG. 55. SPIROGEIRA 
X 60 



WATER SEDIMENT 



143 




FIG. 56. BEGGIATOA 

X 150 




FIG. 57. VOLVOX GLOBATOR 
X 60. (Partly after Cohn) 




FIG. 58. ULOTHRIX 
(After Dodel Port) 




FIG. 59. HUMAN HAIR 
X 100. (adnat. T.G.S.) 




FIG. 60. DOG'S HAIR 
x 100. (adnat. T.G.S.) 



144 



MICROSCOPY 




FIG. 6l. COW'S HAIR 
X ioo. {adnat. T.G.S.) 



FIG. 62. RABBIT'S HAIR 
X 100. {adnat. T.G.S.) 




a b 

FIG. 63. AMOZBA 

X 200 

(a) Motile. (b) Resting 



FIG. 64. PARAMECIUM COLI 
X 400. (T.G.S.) 




FIG. 65. DAPHNIA 



WATER SEDIMENT 



145 




FIG. £6. OVA OF VARIOUS WORMS 
X 400. (After Leuchart) 



a. Ascaris hmibricoides 

b and c. Oxyuris vermictilaris 

d. Distoma hepaticum 

e. Distoma lanceolatuni 

f. Trichocephalus dispar 



g, Anchylostoma duodenal e 
h. Bothriocephahis latus 
i. Tcenia mediocanellata 
k. Tcenia solittm 
/. Ascaris mystax 



MEAT INSPECTION 

The inspection of meat is often part of the practical examina- 
tion of the D.P.H. candidate, and he is required to be able to 
decide if the meat shown to him is fit for human consumption. 

Characters of Good Meat 

Meat when good and fresh should have a marbled appearance, 
due to streaks of fat between the bundles of muscle fibres. The 
colour should be bright and not too dark, and the surface of the 
meat should be glossy and not dull. Beef is always darker than 
mutton, veal, or pork — chiefly for the reason that sheep, calves 
and pigs are bled more freely than oxen at the time of killing. 
The older the animal, the darker and tougher is the flesh. The 
connective tissue should be glistening and firm. The diaphragm 
should be firm, and the abdominal and thoracic parietes 
should show no evidence of adhesions or staining. The pleura 
should be intact. The bone-marrow should be set and be light 
red : the spleen, kidneys, and liver should be regular, of a good 
red, and without variations in colour. 

Good meat is firm and elastic, and does not pit nor crackle on 
pressure. It is juicy, but not wet ; and the juice which adheres 
to the fingers should be of a bright red colour. The fat is hard 
and dry, but feels greasy. The kidneys, spleen and liver are 
firm. All lymphatic glands should be firm. 

The smell of sound meat is well known and characteristic. 
In order to test this more efficiently, the meat should be pierced 
with a clean knife or skewer in the direction of the bone, and 
the implement smelt immediately upon its withdrawal. 

Good meat gives an acid reaction with litmus paper. 

Good meat, when dried upon a water bath, does not lose more 
than 75% by weight. 

Characters of Bad Meat 

Meat that is bad is often soft and watery, some parts are 
harder than others, and there may be emphysematous crackling. 

146 



CHARACTERS OF BAD MEAT 147 

The fat may be liquid or soft, highly coloured or even hemor- 
rhagic. A deep dark purple colour is seen in meat when the 
animal has died without being bled, or when some pulmonary 
congestion or acute septicaemia has affected the animal. The 
lymphatic glands in bad meat may be enlarged, congested, 
hemorrhagic, caseating or calcified. The pleura, peritoneum, or 
viscera may show evidence of disease such as tuberculosis. Pus 
may be present between the muscle fibres. The carcass may 
show signs of emaciation. The odour may be that of putre- 
faction, and the meat may be alkaline in reaction. In advanced 
putrefaction the meat may become a greenish tint. 

Test for Putrefaction. A mixture is prepared containing 
1 part of HC1, 1 part of ether, and 3 parts of alcohol. A few 
c.c. of this are placed in a cylinder, which is then shaken so as 
to distribute the reagent over the sides of the glass. A piece of 
the putrid meat is suspended by a wire inside the cylinder. 
The white fumes of ammonium chloride will appear if the meat is 
in a state of putrefaction. 

Meat may be unfit for human consumption from one 
or more of several causes. 

1. The animal may have been suffering from a disease which 
can be communicated to man by ingestion of the meat. 

2. The animal may have been suffering from a disease which, 
though non-communicable to man, may render the meat un- 
wholesome and liable from its contained toxins to produce 
gastro-enteritis in the consumer. 

3. The meat, though derived from a healthy animal, may 
have undergone decomposition. 

4. The meat may not be of the character stated — e.g. horse- 
flesh may be sold as beef. 

Consideration will now be given to certain diseases of animals, 
which render the whole or parts of the carcass unfit for human 
consumption. 

Anthrax. Anthrax meat rarely comes into the market. The 
animal afflicted usually dies so quickly that it is impossible to 
have it slaughtered. The spleen, liver and kidneys are engorged 
with blood, the intestines are haemorrhagic, the blood is fluid 
and the bacillus anthracis is found in vast quantities in the blood 
and viscera. Of course, all the meat from an anthrax- affected 
animal must be destroyed — preferably by cremation. 

Actinomycosis generally affects the tongue, lower jaw, and 
lungs. The tongue is wooden in consistence, and may show 



148 MEAT INSPECTION 

flattened white nodules on the dorsum. Occasionally abscesses 
are formed, and the pus contains grey granules which show 
typical characters of the " ray fungus " under the microscope. 
If the disease is not widespread, only the affected parts may be 
removed, and the remainder of the carcass passed for eating 
purposes. 

Tuberculosis. It should be remembered that tuberculosis 
in cattle does not frequently lead to pus formation. The tubercles 
remain firm and typical although the whole body may be filled 
with the disease. No part of the body is exempt from tuber- 
culosis, although the lungs and lymphatic glands are the sites 
most commonly infected. The Royal Commission on Tuber- 
culosis in 1898 made the following recommendations with regard 
to tuberculous meat : — 

That the whole carcass should be condemned if — 

1. There is miliary tuberculosis in both lungs. 

2. If there is tuberculosis of both pleura and peritoneum. 

3. If there is tuberculosis of the muscles or of the lymphatic 
glands situated in the muscles. 

4. If tuberculosis lesions exist in any part of an emaciated 
carcass. 

And that the affected parts only should be condemned if — 
i. The lesions are confined to the lungs and the thoracic 
lymphatic glands. 

2. If the lesions are confined to the liver. 

3. If the lesions are confined to the pharyngeal lymphatic 
glands. 

4. If the lesions are confined to any combination of the above ; 
but are collectively small in extent. 

The Commission further recommends that the whole carcass 
of a pig should be condemned if tuberculosis is present even to 
a slight degree; and that foreign meat, in which the pleura 
has been " stripped " should be regarded as tuberculous and 
should be condemned. 

Septicaemia. — In the flesh of an animal dead of septicaemia 
the blood is fluid and extravasated here and there. The organs 
will be engorged and the causative micro-organism will be found 
in the heart blood and generally in the spleen. Local abscesses 
may be present ; and the flesh will not set, will be moist, and 
appear purple in colour. Such meat will decompose rapidly. 
The whole carcass must be condemned. 

Glanders affects horses, and not cattle and sheep. Horse- 



CHARACTERS OF BAD MEAT 149 

flesh infected with glanders is entirely unfit for human consump- 
tion, as the disease is communicable to man. 

Trichinosis. Meat affected with the trichina spiralis is seen 
to be speckled with minute white or grey dots : they are found 
especially in the diaphragm. The pig is more affected than 
cattle and sheep. In order to examine the meat, small portions 
are teased out in dilute potash solution and examined under the 
low power of the microscope : the small coiled worms are easily 
distinguished. An account of them is given later under the 
heading of Parasites of Meat. 

As trichinosis is communicable to man, the carcass of the 
infected pig or other animal must be condemned. 

Cysticercus. Pigs, cattle and sheep all suffer from cysti- 
cercus : the younger animals chiefly are affected, and their flesh 
is found to be pale and studded with small cysts. These cysts 
contain the scolex of what, in the second host, would be the tape 
worm. These are considered later. 

All meat that is infected with cysticercus must be considered 
unfit for human consumption. 

Sheep Rot is caused by the distoma hepaticum invading 
the portal system. In early stages of the disease it is necessary 
only to condemn the affected liver : later, however, the animal 
may become jaundiced and cedematous ; and then the whole 
carcass must be considered as unfit for food. 

The strongylus filaria is found in the lungs of sheep. If the 
animal is not emaciated the carcass need not be condemned on 
this account. 

Symptomatic Anthrax (quarter-ill, etc.) and Malignant 
Oedema are septicsemic diseases caused by anaerobic bacilli. 
Animals so affected die quickly. Their flesh is unfit to eat. 
The symptoms of disease resemble generally anthrax and other 
septicaemic conditions, and the meat shows the same general 
characteristics. 

Swine Fever. This disease is very severe among pigs and 
is exceedingly infectious. The flesh in the early stages of the 
disease shows few lesions ; but later a patchy redness of the skin 
appears which can be traced down through the fat into the flesh. 
There is much ulceration of the large intestine and patches of 
congestion or consolidation in the lungs, liver and lymphatic 
glands. The flesh of a pig dead from swine fever, or killed 
during the illness, is not fit for human food, and the whole 
carcass must be destroyed. 



150 MEAT INSPECTION 

Foot and Mouth Disease. The tongue and mucous mem- 
brane of the mouth and pharynx show vesicles and ulceration. 
The feet also show the same condition of ulcers and vesiculation, 
and the hoofs may be loose, or may even fall off. The disease is 
very infective, and the carcasses must be condemned. 

Horse-flesh is darker in colour than beef, the grain is more 
coarse, and the fat is more yellow and soft. The bones are 
stronger in the horse than in the ox, and have better-marked 
ridges for the insertion of muscles. The tongue of the horse is 
rounded and smooth : that of the ox is pointed and rough. 
The liver of the horse has three large lobes and one small one 
and no gall bladder. The liver of the ox has one large and one 
small lobe. The kidney of the horse is heart-shaped : that of 
the ox is long and lobulated. The heart of the ox contains a 
bone, the os cordis ; there is no bone in the heart of the horse. 

Fish. Fresh fish should have bright gills and prominent eyes, 
and their flesh should be firmly adherent to the bones. They 
should not pit on pressure, nor should their tails hang down 
unduly. They should give only their characteristic smell. 

Inelasticity of the flesh, and an unpleasant odour, are sure signs 
of decomposition in fish. Fresh fish will sink in water ; bad fish 
floats. 

Any fish that is not quite fresh should be considered unfit for 
food. Fish decomposes rapidly, and even slightly tainted fish 
may give rise to very severe gastro-enteritis. 

Parasites of Meat 

Trichina spiralis. This parasite is found affecting man 
almost throughout the whole world, especially where much pork, 
and more especially uncooked pork, is eaten. 

The natural host would appear to be the rat, and the disease 
is kept up in them owing to the habit of eating their dead. Pigs 
become affected by eating portions of dead rats or the refuse of 
slaughtered pigs, to which they frequently have access. Man 
acquires it through eating trichinosed pork. 

The male measures 12 to 1*5 mm. and the unimpregnated 
female 1*5 to 2*0 mm. 

The anterior end is finely pointed and surmounted with the 
punctiform mouth. 

The female has a single ovarian tube which opens into the 
vagina on the ventral surface about two-fifths of the length of 



PARASITES OF MEAT 



151 



the worm from the mouth. After copulation the male dies and 

the female increases in size to 3 to 4 mm. 

The young trichinae leave their shell 
while still in the uterus, and are born free, 
some five or six days after impregna- 
tion. Several thousands are produced 
before the female dies and is voided. 

The young embryo measures about 
o'i mm. and is endowed with activity. 
Shortly after birth they pierce the 
intestinal wall, cross the peritoneal 
cavity by the connective-tissue spaces 
and so reach the muscles and other 
tissues. As they proceed they increase 
in size, and signs of development are 





FIG. 67. TRICHINA SPIRALIS 

a. Female voiding complete 
embryos, b. Male 
X 80. (After Leuchart) 



FIG. 68. TRICHINA SPIRALIS 

Larval form encysted in 

muscular fibre 

X 80. (After Leuchart) 



found. At the end of 10 days or less they arrive at their 
destination in the connective-tissue spaces of the muscles, etc. 

Their presence gives rise to irritation and subsequent prolifera- 
tion of the connective-tissue cells in the immediate neighbour- 
hood. The proliferation on the one hand, and the movement of 
the trichina on the other, lead eventually to the formation of a 
cyst and wall. At the end of about 18 days the trichina has 



152 MEAT INSPECTION 

increased in size and coiled itself up, and the encystment is 
complete. 

The cysts lie with their long diameter parallel to the muscle 
fibres and are filled with clear albuminous fluid, whilst the larval 
trichina lies coiled up but in contact w T ith the wall — especially 
when alive. It now measures about i mm. in length, and is 
provided with a mouth, alimentary canal and anus, as well as 
rudimentary sexual organs. 

In this condition it remains alive sometimes for years, and is 
capable, under favourable circumstances, of developing fully. 
At the end of a certain time, however, if the flesh of the host is 
not consumed, fatty and calcareous degeneration sets in and the 
larva dies. 

The affected meat can be seen by the naked eye to be 
11 measly," and in order to examine the trichina the muscle fibres 
containing a cyst should be teased out gently in potash, mounted 
in potash or water, and a coverslip gently pressed down on the 
scrapings. 

Beautiful specimens can be obtained by hardening the tissue 
and cutting sections of it. 

Taenia mediocanellata (Synonym T. saginata^ Ttzniarhynchus 
mediocanellatus). This is perhaps the commonest and most 
widely distributed of all human tape worms. It is found in 
Europe, Asia, Africa, America, and Australia. In this country it 
is by far the most common, the Tcznia solium being decidedly 
rare. 

It measures from 4 to 8 metres, and consists of from 1200 to 
1300 proglottides. Those near the head are quite small, and 
gradually enlarge both in length and breadth until near the 
middle of the worm they measure about 14 mm. square, and are 
only 2 mm. thick. As the distal end is approached they become 
narrower, longer, and thicker. As they break away from the main 
body they are endowed with movement. 

The head is somewhat pear-shaped, and measures from 1 *s to 
2 mm. in breadth. It is furnished with four suckers, but has 
neither hooklets nor rostellum. 

The genital pore of the proglottis is marginal, and frequently 
projects. This leads to the uterus, which is linear, and lies in 
the long axis of the worm, and which has 20 or 30 lateral 
branches, which divide dichotomously. 

The eggs are contained in the uterus, and when the proglottis 
is ripe consist of the embryo enclosed in a shell, which is thick, 



PARASITES OF MEAT 



153 



and is composed of innumerable little rods. The egg is dis- 
tinctly oval, and is 0*03 mm. in length. The embryo possesses 
the six hooks. 

The ox is generally the intermediate host. This animal 
swallows the eggs, and the digestive juices dissolve the envelope 
and set free the embryo, which promptly bores its way into the 
muscles. It now discards its hooks, and develops the head at 





FIG. 71 



(a) T^NIA MEDIOCANELLATA 
Head X 20. {ad nab T.G.S.) 

(0) PROGLOTTIS, SHOWING NUMEROUS DICHOTOMOUS 

BRANCHES OF THE UTERUS 

Semi-diagrammatic 

{c) EGG, SHOWING EMBRYO 
X 400 



the opposite end, whilst the rest of the body becomes a small 
bladder. The whole cysticercus lies between the muscular fibres 
and measures from i cm. in length. From one end of the short 
diameter of the cyst the head of the cysticercus may be made to 
protrude by placing it in warm water. It is seen under the 
microscope to be an exact reproduction of the head and neck of 
the mature worm. 

The cysticercus is not known in the human subject. 

Man is infected undoubtedly from eating underdone beef 



154 



MEAT INSPECTION 



affected with cysticerci; quite a low temperature (50° C.) has been 
found sufficient to render the cysticerci harmless. 

The Tcenia solium. This tape worm is found wherever swine 
are badly kept or where the pork is improperly cooked. Hence 
it is comparatively common in North Germany, and uncommon 
in this country. It is smaller than the T. mediocanellata, rarely 
measuring 4 m. The proglottides resemble those of the T. medio- 
canellata in shape in the various parts of the body, but are 
smaller, being not more than 8 mm. broad in the broadest part. 
The genital pore is marginal, and leads to a linear uterus which 
has 8 or 10 lateral branches which divide dendritically. 

The eggs are more spherical than those of the T. mediocanellata^ 
but otherwise resemble them. The head is more or less spherical 
with a diameter of 1 *o mm. It has four suckers and a rostellum, 
which can be protruded. The rostellum carries a double row of 
hooklets numbering 28 in all. 

The life-history and cysticercus form is similar to that of the 
T. medio canellata^ except that the pig is the intermediate host. 

It differs, however, in that this cysticercus is occasionally found 
in man. 

It is extremely rare to find more than one T. medioca?iellata in 
the same patient, but numerous cases have been recorded in 
which two or more T. so Ha have been found. 

Bothriocephalus latus. This parasite — the largest met with 
in the human subject — is not of very wide distribution. It is 






fig. 72. bothriocephalus latus : (a) lateral, (b) front view of head 

( x 10) ; {c, d y and e) proglottides in the upper, middle, and lower 

parts of the worm (nat. size). (After Leuchart) 

found in people inhabiting the Franco-Swiss lakes, the Baltic 
shores, Japan, etc. 

It measures from 6 to 12 or even 16 metres in length. 

The proglottides are broad and short. The genital pore is in 
the centre of the proglottis and not marginal as in most others, 



PARASITES OF MEAT 155 

and the uterus is rosette -shaped. Each segment is herma- 
phrodite. 

The head is flattened and shaped like an olive or blunt almond. 
It has two lateral suctorial grooves in place of suckers, and has 
neither rostellum nor hooklets. 

The eggs are oval with a long diameter of about 0*05 mm., 
the shell is simple, brown, and closed at one end by an oper- 
culum. 

When the proglottides break away, the ova do not contain the 
mature embryo enclosed in a shell as in the other tape worm, but 






fig. 73 

PROGLOTTIS OF BOTHRIOCEPHALUS 

LATUS, SHOWING ROSETTE UTERUS 

X 4. (After Leuchart) 



a b 

FIG. 74 
EGGS OF BOTHRIOCEPHALUS 
LATUS : (a) containing em- 
bryo ; {b) empty 
X 200. (After Leuchart) 




merely a partially developed egg. These, in order to attain 
maturity, must remain in water for some time, when the ripe 
embryo, a ciliated six-hooked one, emerges from the shell by 
opening the operculum. It then swims about in the water. 
This is either eaten by fish, or by some animal 
which is subsequently consumed by fish. From 
the intestine of the fish the embryo makes its way 
into the muscles, where it loses its cilia and 
hooklets, and elongates. After a time evidences 
of the two suctorial grooves are found and the FIG . 75 . FU lly 
embryo attains to the size of 1 or 2 cm. ; there developed em- 
is no cysticercus form as described in other 
tape worms, the embryo sometimes lying almost 
free between the muscular fibres. From the 
imperfectly cooked or raw fish the embryo is 
transferred to the intestine of man, dog, cat, etc. 
develops into the mature worm. 

The Distoma hepaticum. This worm is exceedingly common 
in the livers of sheep, less common in cattle, sometimes in the 
horse, rabbit, and even in man. 



BRYO OF BOTH- 
RIOCEPHALUS 
LATUS 
(After Leuchart) 



where it 



156 MEAT INSPECTION 

It is leaf-shaped and flat, being about three or four times as long 
as it is broad, and varies in length from 16-40 mm. 

The worm is enclosed by a skin bearing minute spines attached 
to the transparent epidermis, and more numerous at the cephalic 
end. The true skin consists of dense fibrous tissue. 

It possesses two suckers, one at the anterior end, that com- 
municates with the mouth and pharynx, and the other, which is 
placed centrally above the junction of the upper and middle 
thirds, is blind. These suckers inter alia appear to be used for 
locomotion. 

Below the circular pharynx is a band of circular muscular 
fibres which acts as a sphincter, and prevents the regurgitation of 
food from the oesophagus, which is a short prolongation of the 
pharynx, and divides into two canals a little above the ventral 
sucker. These two canals run parallel to the sides, and give off 
a series of branches externally, which again divide. A few short 
branches are given off internally. All these branched tubes 
terminate abruptly in the parenchymatous tissue, and have no 
external opening. 

The excretory or water vascular system consists of a central 
canal, which extends from the junction of the upper and middle 
thirds to the posterior extremity, where it terminates in a small 
opening, the foramen caudate. The anterior end possesses three 
distinct branches, two lateral and one — a small one — mesial. 
The main trunk, as well as the three primary branches, all give off 
smaller branches, which divide dendritically right up to the margin 
of the worm. 

The worm is hermaphrodite. There is a genital pore situated 
just above the ventral sucker. Into this pore the penis protrudes. 
The penis is lodged in a pouch, which also encloses the recepta- 
culum seminis. This latter receives the junction of the two vasa 
differentia, which are formed by the junction of the seminiferous 
tubules coming from the testes. 

The testes are not globular masses, but consist of a large 
number of vermiform tubes, which are spread out in the middle 
of the ventral portion of the worm. 

The orifice of the vagina is very small, and is situated in the 
genital pore close to the penis. Just behind the orifice, the 
vagina widens out into a uterus which is much coiled, and lies 
between the ventral sucker and the junction of the upper and 
middle thirds of the body, i.e. above the testes. In the uterus 
can be seen a large number of ova in various stages of develop- 



PARASITES OF MEAT 157 

ment. At the ovarian end the uterus suddenly contracts, and is 
connected with a tube which suddenly bifurcates, the branches 
passing laterally across the body and suddenly bending down- 
wards near the lateral margin, to which they run parallel. These 
tubes give off branches ending in grape-like ca?cal extremities, 
the yolk sacs. These sacs contain minute nucleated cellules. 

The ovum when discharged from the uterus is oval and 
measures 0*14 mm. in length and o*n mm. in breadth. It con- 
tains a fully developed embryo. This embryo has the form of 
a cone, the anterior end being flatly convex with a central 
proboscis-like papilla, and is completely covered with cilia. The 
ovum is conveyed by the excrement into water or damp soil, and 
here the embryo leaves the shell, and by means of its cilia moves 
about in search of an intermediate host, usually a mollusc or 
crustacean. It bores into this host, loses its cilia and enlarges — 
forming either a sporocyst (a hollow sac without alimentary 
canal) or a redia (a similar structure, but possessing an 
alimentary canal). 

From certain germ cells in the sporocyst or redia, cercaricz 
are developed. These, like the adult distoma, possess suckers 
and alimentary canal \ but, unlike them, they have no genital 
organs, and have an active and powerful tail. When they are 
developed they leave the sporocyst or redia and the body of the 
intermediate host and become free, either in the water or damp 
soil. The cercaria now either seeks a second intermediate host 
and becomes encysted, or is taken up by the definite host, where 
it finds its way into the bile ducts, intestine, etc., and rapidly 
develops into the adult hermaphrodite worm. 



158 



MEAT INSPECTION 




FIG. 76. DISTOMA 

HEPATIC UM 

Nat. size. (After Leuchart) 




FIG. 77. DISTOMA HEPATICUM 
Left half showing the alimentary system, 
right half showing the excretory system 
(adapted) 





FIG. j8. EGGS OF THE DISTOMA HEPATICUM 
X 200 




FIG. 79. FREE SWIMMING EMBRYO 
OF DISTOMA HEPATICUM 




FIG. 80. CERCARIA FORM 
OF DISTOMA HEPATICUM 



APPENDIX 

CHEMICAL SYMBOLS AND APPROXIMATE ATOMIC 

WEIGHTS OF SOME OF THE ELEMENTARY 

BODIES 



Aluminium 


. Al 


27-5- 


Manganese . 


Mn .. 


55'° 


Arsenic 


. As 


•• 75*o 


Mercury 


Hg .. 


200*0 


Barium 


. Ba 


•• i37'° 


Nitrogen 


N .. 


14*0 


Calcium 


. Ca 


40*0 


Oxygen 


. 


16*0 


Carbon 


. C 


I2*0 


Phosphorus . 


P .. 


310 


Chlorine 


. CI 


•• 35'5 


Potassium 


K .. 


39'° 


Copper . 


. Cu 


63-2 


Silver . 


Ag .. 


108*0 


Hydrogen 


. H 


I'O 


Sodium . 


Na .. 


23*0 


Iodine . 


. I 


126*6 


Sulphur 


S .. 


32*0 


Iron 


. Fe 


56*0 


Tin 


Su .. 


. n8*o 


Lead . 


. Pb 


.. 206*5 


Zinc 


Zn .. 


65*0 


Magnesium 


. Mg 


24*0 










WEIC 


iHTS AN 


D MEASURES 




i gramme = 


iS'43 2 g ] 


'ains. 


1 square metre 


= 10*764 square 


i litre = 


iooo cut 


)ic centi- 




feet 






metres 




1 cubic metre 


= 1000 


litres. 




35'3 flui c 


1 ounces. 




= 35*3 


cubic 




61*027 c 


ubic 




feet 






inches. 




1 cubic foot 


= 6*23 


gallons. 


i metre 


= 39*37 in 


ches. 


1 kilogram 


= 2*204 


pounds. 



159 



160 APPENDIX 




ALCOHOL TABLES. (After Allen) 




Specific gravity taken at 15*5° C. 




Absolute Alcohol — percentage by weight x r 26 gives percentage 


by volume. 




Alcohol 




Alcohol 


Specific percentage 


Specific 


percentage 


gravity. by weight. 


gravity. 


by weight. 


•79384 ... ... IOO'OO 


•879 


67*13 


797 9 8 *97 


•882 


65*83 


*8oo ... ... 98*03 


•884 


65*00 


803 97'°3 


•886 


64*13 


•806 ... ... 96*03 


•889 


62*82 


•809 94-97 


•891 


61*92 


•812 93-92 


•893 


61 -08 


•815 ... .. 92*81 


•896 


59 83 


"817 ... ... 92*07 


•898 


58-95 


•820 ... ... 91*00 


•900 


58*05 


•823 89-92 


•902 


57*21 


•826 88-76 


•905 


55-86 


•828 87-96 


•907 


54*95 


•831 86-8i 


•909 


54*00 


•833 86-04 


•911 


53-13 


•836 84*88 


•914 


5!*79 


•8382 ... ... 84*00 


'916 


50*96 


•841 .. ... 82*92 


•918 


50-09 


•843 82-15 


•919 


49-24 


•846 80-96 


•920 


48-96 


•848 80-13 


•922 


48-05 


•851 78*92 


•925 


46*91 


•853 78*12 


•927 


46*00 


•856 76-88 


•929 


45*09 


•858 76*04 


•931 


43*95 


•860 ... ... 75-14 


*933 


43 -oo 


'^3 7379 


'935 


42*05 


•865 ... ... 72*96 


'937 


41-05 


•867 ... ... 72*09 


*939 


40*05 


•870 ... ... 70*84 


•941 


39*°5 


•872 ... ... 70*04 


*943 


37*94 


'874 69*21 


*94S 


37-11 


•877 67*96 


•947 


36*00 





APPENDIX 


161 




Alcohol 




Alcohol 


Specific 


percentage 


Specific 


percentage 


gravity. 


by weight. 


gravity. 


by weight. 


•949 


35*°° 


•977 


I5'°° 


•951 


34*05 


•978 


14*00 


*953 


32-87 


•980 


i3' 00 


'954 


31-94 


•981 


I2'00 


•956 


31-00 


•982 


I I 'OO 


•958 


29-87 


•983 


9'99 


•959 


28-87 


•985 


8-89 


•961 


2 7*93 


•986 


7*99 


•962 


26-87 


•988 


7*02 


•964 


2586 


•989 


6'02 


•965 


25-00 


■991 


5'oi 


•966 


24*00 


•992 


4'S 1 


•967 


23*00 


'993 


3'49 


•969 


22*00 


"994 


3*° 2 


•970 ... - 


2 1*00 


'995 


2, 5! 


•971 


20*00 


•996 


i "99 


•972 


I9'00 


•997 


* 5 1 


•974 


18-00 


•998 


1 02 


'975 


17*00 


•999 


°'53 


•976 


16*00 


I'OOO 


O'OO 



INDEX 



Acarus farinee, 122 

— scabei, 139 
Actinomycosis, 147 
Air Analysis, 95-105 

— Carbon Dioxide in, 97 

— Carbon Monoxide in, 100 

— Ground, no 

— Noxious Gases in, 104 

— Oxygen in, 95 

— Ozone in, 104 
Alcohol, Estimation of, 90 
Algae in Water, 5 

Alum in Bread, 87 

Ammonia, Albuminoid, 16, 37, 49, 

51 . 
Ammonia, Free and Saline, 13, 37, 

49, 51 

Anquillula aceti, 123 
Anthrax, 147 

— Symptomatic, 149 
Antimony, Test for, 93 
Antiseptics in Milk, 74 
Arachnida, 139 
Arsenic, Test for, 93 
Aspergillus, 124 
Available Chlorine, 112 

B 
Beer, 92 

— Arsenic in, 93 
Bleaching Powder, 1 1 1 
Boric Acid, Tests for, 74 
Bothriocephalus latus, 154 
Bread, 85 

— Acidity in, 86 

— Alum in, 87 
Bruchus pisi, 122 
Butter, 75-83, 128 

— Adulteration of, 77 

— Preservatives in, 8^ 



Butter, Salt in, 77 

— Water in, 76 

Butter-Fat, Specific gravity of, 78 

— Insoluble acids in, 83 

— Volatile acids in, 80 



Calandra granaria, 121 
Carbolic Acid Estimation, 112 
Carbon Dioxide in Air, 97 
Carbon Monoxide in Air, 100 
Chalk Waters, 42 
Chicory, 88, 129 
Chlorides, Estimation of, 7 
Chlorine Available, 1 1 1 
Cimex lectularius, 137 
Claviceps purpurea, 126 
Clothing, 132 

Coal measures, Water from, 44 
Cocoa, 131 
Coffee, 87, 128 
Coir, 135 

Collection of water samples, I 
Cotton, 133 
Copper in Water, 28 
Copper-Zinc Couple, 23 
Cysticercus, 149 

D 

Disinfectants, 111-115 
Distoma hepaticum, 155 

E 

Ergot, 85, 126 

Examinations, Practical work in, 48 



Fish, 150 
Flax, 133 
Flour, 83 



162 



INDEX 



163 



Flour, Composition of, 83 

— Ergot in, 85 

— Gluten in, 84 

— Mineral Matter in, 85 
Foot and Mouth Disease, 150 
Formalin, Tests for, 75 

G 

Gases in Water, 32 
Gluten, Estimation of, 84 
Greensands, Waters from, 43 
Ground Air, 113 

H 

Hardness in Water, Estimation of, 9 
Hemp, 134 
Hempel's Bulbs, 95 
Horse-flesh, 150 
Human Parasites, 136 



Indigo Method, 21 

Insecta, 136 

Interpretation of Water Analyses, 

35-48 

Iron in Water, 29 



Jute, 134 



J 



K 



Kjeklahl's Method, 52 

L 

Lead in Water, 27, 31 
Lemon Juice, 94 
Lime Juice, 94 
Limestone, Water from, 44 
Linen, 133 

M 

Meat, 146-158 

— Bad, 147 

— Good, 146 
Microscopy, 1 16-145 
Milk Analysis, 65-75, 127 

— Adulteration of, 71 

— Ash, 69 

— Composition of, 65 

— Dirt in, 127 



Milk Fat, 69 

— Preservatives in, 73 

— Specific Gravity of, 66 

— Total Solids, 67 
Mucor, 124 

N 

Nessler's Reagent, Use of, 14 
Nitrates, Estimation of, 20 

— Tests for, 19 
Nitrites, Estimation of, 18 

— Tests for, 17 
Noxious Gases in Air, 104 

O 

Oolite, Water from, 44 
Ova of Worms, 145 
Oxalic Acid Standard, 99 
Oxygen, Absorbed, 24 

— Dissolved in Water, 32 

— in Air, 97 



Paper, 134 

Parasites, Human, 136 

— of Grain, 121 

— of Meat, 150 
Pediculi, 138 
Penicillium glaucum, 123 
Pernosporon, 125 
Phenol estimation, 112 
Poisonous Gases in Air, 104 
Practical Work, Scheme of, 48 
Puccinia grammis, 125 

Pulex irritans, 137 
Pulex penetrans, 137 
Putrefaction, Test for, 147 

R 

Rain Water, 40 

Reagents, Preparation of, 56-65 

Reichert-Wollny Process, 80 

Reinsch's Test, 93 

River Waters, 45 

Rye Ergot, 126, 85 

Rye Starch, 118 

S 

Salicylic Acid, Test for, 74 
Sandstone, Water from, 44 
Sarcopsylla, 137 



1 64 

Sarcoptes scabei, 139 
Septicemic Meat, 148 
Sewage Analysis, 50-56 

— Ammonia in, 51 

— Chlorides in, 50 

— Dissolved Oxygen in, 52 

— Effluents, 54 

— Effluents, Standards for, 54 

— Nitrates in, 52 

— Nitrites in, 52 

— Oxygen absorbed by, 52 

— Total Nitrogen of, 52 

— Total Solids of, 50 
Sheep Rot, 149 
Silk, 136 

Soap, 10 

Soil, Analysis of, 106-109 
Spirits, Analysis of, 89 
Standard Solutions, 59-65 
Starch of Arrowroot, 118 

Barley, 118 

Bean, 120 

Maize, 120 

Oats, 120 

Pea, 119 

Potato, 118 

Rice, 120 

Rye, 118 

Sago, 121 

Tapioca, 121 

Wheat, 117 

Starches, Mounting of, 116 
Surface Waters, 41, 46 
Swine Fever, 149 
Symptomatic Anthrax, 149 



Taenia Mediocanellata, 152 
Tea, 130 
Ticks, 141 
Tidy's Process, 24 
Tilletia caries, 126 
Total Solids in Water, 6 

Milk, 67 

— — — Sewage, 50 
Trichina spiralis, 150 
Trichinosis, 149 
Tuberculosis, 148 
Tylenchus tritici, 122 



INDEX 



u 



Ustilago carbo, 126 
Ustilago segetum, 125 



V 



Valenta Test, 79 
Vinegar, 93 

W 

Wat -r Analysis, 1-50 

— Aeration of, 5 

— Algae in, 5 

— Albuminoid Ammonia in, 16, 37 

— Free Ammonia in, 13, 37 

— Chlorides in, 7, 36 

— Collection of Samples, 1 

— Colour of, 4 

— Copper in, 28 

— from Chalk, 42, 47, 48 

Coal Measures, 44 

Greensand, 48 

Limestone, 44 

Oolite, 44 

Sandstone, 44 

Subsoil, 42, 46, 47 

Surface, 41, 46 

— Iron in, 29 

— Nitrates in, 20, '8 

— Nitrites in, 18, 38 

— Oxygen absorbed by, 24, 39 

— Permanent Hardness of, 12 

— Physical Characters, 4, 35 

— Rain, 40 

— Reaction of, 5, 36 

— Report, 3 

— River, 45 

— Sediment, 5, 141 

— Smell of, 5 

— Taste of, 4 

— Total Hardness of, 9, 36 

— Total Solids in, 6, 35 

— Turbidity in, 4 

— Volatile Solids in, 7 

— Zinc in, 30 
Wines, Analysis of, 91 
Winkler's Method, 32 
Wool, 135 

Z 
Zinc in Water, 30 



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cloth. 1225 pp. net, $15.00 

Vol. II. Sulphate of Soda, Hydrochloric Acid, Leblanc 
Soda. Third Edition, much enlarged. In two parts, 
not sold separately. 335 illustrations. 8vo. cloth. 
1044 pp. net, $15.00 

Vol. III. Ammonia Soda. Various Processes of Al- 
kali-making, and the Chlorine Industry. 181 illus- 
trations. 8vo. cloth. 784 pp. net, $10.00 

Vol. IV. Electrolytical Methods. In Press. 

LTJQTJEUR, L. M. Minerals in Rock Sections. The 

practical methods of identifying them with the micro- 
scope. Third Edition. 86 illustrations. 8vo. cloth. 
150 pp. net, $1.50 

MARTIN, G. Triumphs and Wonders of Modern Chem- 
istry. A popular treatise on modern chemistry and 
its marvels written in non-technical language. j6 il- 
lustrations. i2mo. cloth. 358 pp. net, $2.00 

MELICK, CHARLES W. Dairy Laboratory Guide. 52 

illustrations. i2mo. cloth. 135 pp. net, $1.25 



LIST OF CHEMICAL BOOKS 



MERCK, E. Chemical Reagents : Their Purity and Tests. 
8vo. cloth. 250 pp. net, $1.50 

MILLER, E. H. Quantitative Analysis for Mining En- 
gineers. Second Ed. 8vo. cloth. 158 pp. net, $1.50 

MOSES, A. J., and PARSONS, C. L. Elements of Mineral- 
ogy, Crystallography, and Blowpipe Analysis from a 
Practical Standpoint. Fourth Edition. 583 illustra- 
tions. 8vo. cloth. 448 pp. net, $2.50 

MTJNBY, A. E. Introduction to the Chemistry and 
Physics of Building Materials. Illus. 8vo. cloth. 365 
pp. (Van XostrancTs Westminster Series.) net, $2.00 

MURRAY, J. A. Soils and Manures. 33 illustrations. 
8vo. cloth. 367 pp. (Van Nostrand's Westminster 
Series.) net, $2.00 

NAQTJET, A. Legal Chemistry. A guide to the detec- 
tion of poisons as applied to chemical jurisprudence. 
Translated, with additions, from the French, by J. P. 
Battershall. Second Edition, revised with additions. 
i2mo. cloth. 190 pp. $2.00 

0LSEN, J. C. A Textbook of Quantitative Chemical 
Analysis by Gravimetric and Gasoinetric Methods. 

Including 74 laboratory exercises giving the analysis 
of pure salts, alloys, minerals and technical products. 
Fourth Edition, revised and enlarged. 74 illustrations. 
8vo. cloth., 576 pp. net, $4.00 

PARRY, ERNEST J. The Chemistry of Essential Oils 
and Artificial Perfumes. Second Edition, thoroughly 
revised and greatly enlarged. Illustrated. 8vo. cloth. 
554 pp. net, $5.00 



8 D. VAN NOSTRAND COMPANY'S 

PERKIN, F. M. Practical Methods of Inorganic Chem- 
istry. Illustrated. i2mo. cloth. 152 pp. net, $1.00 

PHILLIPS, J. Engineering Chemistry. A practical 
treatise. Comprising methods of analysis and valua- 
tion of the principal materials used in engineering 
works. Third Edition, revised and enlarged. Illus- 
trated. i2mo. cloth. 422 pp. net, $4.50 

PLATTNER'S Manual of Qualitative and Quantitative 
Analysis with the Blowpipe. Eighth Edition, revised. 
Translated by Henry B. Cornwall, assisted by John 
H. Caswell, from the Sixth German Edition, by Fried- 
rich Kolbeck. 87 ill. 8vo. cloth. 463 pp. net, $4.00 

PRESCOTT, A. B. Organic Analysis. A manual of the 
descriptive and analytical chemistry of certain carbon 
compounds in common use. Sixth Edition. Illus- 
trated. 8vo. cloth. 533 pp. $5.00 

PRESCOTT, A. B., and JOHNSON, 0. C. Qualitative 

Chemical Analysis. Sixth Edition, revised and en- 
larged. 8vo. cloth. 439 pp. net, $3.50 

PRESCOTT, A. B., and SULLIVAN, E C. First Book in 
Qualitative Chemistry. For studies of water solution 
and mass action. Eleventh Edition, entirely rewritten. 
i2mo. cloth. 150 pp. net, $1.50 

PR0ST, E. Manual of Chemical Analysis. As applied 
to the assay of fuels, ores, metals, alloys, salts, and 
other mineral products. Translated from the original 
by J. C. Smith. Illus. 8vo. cloth. 300 pp. net, $4.50 

PYNCH0N, T. R. Introduction to Chemical Physics. 

Third Edition, revised and enlarged. 269 illustrations. 
8vo. cloth. 575 pp. $3.00 



LIST OF CHEMICAL BOOKS 



ROGERS, ALLEN. A Laboratory Guide of Industrial 
Chemistry. Illustrated. 8vo. cloth. 170 pp. net, $1.50 

ROGERS, ALLEN, and AUBERT, ALFRED B. Industrial 

Chemistry. Written by a staff of eminent specialists. 
8vo. cloth. Illustrated. In Press. 

ROTH, W. A. Exercises in Physical Chemistry. Author- 
ized translation by A. T. Cameron. 49 illustrations. 
8vo. cloth. 208 pp. net, $2.00 

SCHERER, R. Casein: Its Preparation and Technical 
Utilization. Translated from the German by Charles 
Salter. Second Edition, revised and enlarged. Il- 
lustrated. 8vo. cloth. 196 pp. net, $3.00 

SCHWEIZER, V. Distillation of Resins, Resinate Lakes 
and Pigments. Illustrated. 8vo. cloth. 183pp.net, $3.50 

SCOTT, W. W. Qualitative Chemical Analysis. A labo- 
ratory manual. Illus. 8vo. cloth. 176 pp. net, $1.50 

SEIDELL, A. Solubilities of Inorganic and Organic Sub- 
stances. A handbook of the most reliable quantitative 
solubility determinations. Second Printing, corrected. 
8vo. cloth. 367 pp. net, $3.00 

SENTER, G. Outlines of Physical Chemistry. Second 

Edition, revised. Illus. i2mo. cloth. 401 pp. $1.75 

SEXTON, A. H. Fuel and Refractory Materials. Second 
Ed., revised. 104 illus. i2mo. cloth. 374 pp. net, $2.00 

SMITH, W. The Chemistry of Hat Manufacturing. 

Revised and edited by Albert Shonk. Illustrated. 
i2mo. cloth. 132 pp. net, $3.00 

SPEYERS, C. L. Text-book of Physical Chemistry. 20 
illustrations. 8vo. cloth. 230 pp. net, $2.25 



io D. VAN NOSTRAND COMPANY'S 

STEVENS, H. P. Paper Mill Chemist. 67 illustrations. 
82 tables. i6mo. cloth. 280 pp. net, $2.50 

STJDBOROUGH, J. J., and JAMES, J. C. Practical Or- 
ganic Chemistry. 92 illustrations. i2mo. cloth. 
394 pp. net, $2.00 

TITHERLEY, A. W. Laboratory Course of Organic 
Chemistry, Including Qualitative Organic Analysis. 
Illustrated. 8vo. cloth. 235 pp. net, $2.00 

T0CH, M. Chemistry and Technology of Mixed Paints. 

62 photo-micrographs and engravings. 8vo. cloth. 
166 pp. net, $3.00 

Materials for Permanent Painting. A manual for 

manufacturers, art dealers, artists, and collectors. 

With full-page plates. Illustrated. 121110. cloth. 

208 pp. net, $2.00 

TUCKER, J. H. A Manual of Sugar Analysis. Sixth 
Edition. 43 illustrations. 8vo. cloth. 353 pp. $3.50 

VAN N0STRANDS Chemical Annual, Based on Bieder- 
mann's "Chemiker Kalender." Edited by J. C. Olsen, 
with the co-operation of eminent chemists. Second 
Issue, 1909. i2mo. cloth. net, $2.50 

VINCENT, C. Ammonia and Its Compounds. Their 
manufacture and uses. Translated from the French 
by M. J. Salter. 32 ill. 8vo. cloth. 113 pp. net, $2.00 

VON GE0RGIEVICS, G. Chemical Technology of Textile 
Fibres. Translated from the German by Charles 
Salter. 47 illustrations. 8vo. cloth. 320 pp. net, $4.50 

Chemistry of Dyestuffs. Translated from the Sec- 



ond German Edition by Charles Salter. 8vo. cloth. 
412 pp. net, $4.50 



LIST OF CHEMICAL BOOKS n 

WANKLYN, J. A. Milk Analysis. A practical treatise 
on the examination of milk and its derivatives, cream, 
butter and cheese. Illus. 121110. cloth. 73 pp. $1.00 

Water Analysis. A practical treatise on the exami- 



nation of potable water. Eleventh Edition, revised, by 
W.J.Cooper. Illus. 121110. cloth. 213 pp. $2.00 

WINCHELL, N. H. and A. N. Elements of Optical Min- 
eralogy. An introduction to microscopic petrography. 
350 ill. 4 plates. 8vo. cloth. 510 pp. $3.50 

WINKLER, C, and LUNGE, G. Handbook of Technical 
Gas Analysis. Second English Edition. Illustrated. 
8vo. cloth. 190 pp. $4.00 

W0RDEN, C. E. The Nitrocellulose Industry. A com- 
pendium of the history, chemistry, manufacture, com- 
mercial application, and analysis of nitrates, acetates, 
and xanthates of cellulose as applied to the peaceful 
arts. With a chapter on gun cotton, smokeless pow- 
der and explosive cellulose nitrates. Illustrated. 
8vo. cloth. Two volumes. 1239 pp. net, $10.00 



D. VAN NOSTRAND COMPANY 

Publishers and Booksellers 

23 flURRAY AND 27 WARREN STREETS, NEW YORK. 



SECOND ISSUE, 1909 
12mo. cloth 575 Pages Net. $2.50 



VAN NOSTRAND'S 

Chemical Annual 

A HANDBOOK OF USEFUL DATA 

for analytical, manufacturing and investi- 
gating chemists and chemical students. 
BASED ON BIEDERM ANN'S 'CHEMIKER KALENDER" 

EDITED BY 

Prof. J. C. OLSEN, A.M., Ph.D. 

Polytechnic Institute of Brooklyn ; formerly Fellow Johns Hopkins 
University ; author of " Quantitative Che?nical Analysis " 

WITH THE CO-OPERATION OF EMINENT CHEMISTS 



CONTENTS 

New Tables— Physical and Chemical Constant of the Essential Oils ai.d 
Alkaloids. 

Melting Points and Composition of the Fusible Alloys. 

Density of Carbon Dioxide Polenske Values of Oils, etc. 

Tables for the Calculation of Gravimetric, Volumetric, and Gas Analyses. 

Tables of the Solubility, Boiling and Freezing Points, Specific Gravity, and 
Molecular Weight of the commonly used Inorganic and Organic Com- 
pounds. 

Specific Gravity Tables of Inorganic and Organic Compounds. 
Other Physical and Chemical Constants of Chemical and Technical Pro- 
ducts. 
Conversion Tables of Weights and Measures. 
New Eooks and Current Literature of the Year. 



ALL TABLES WILL BE REVISED ANNUALLY TO GIVE THE 
MOST RECENT AND ACCURATE DATA 



D. Van Nostrand Company 
23 Murray and 27 Warren Sts., New YorK 



